diff --git a/src/aeso_aci.erl b/src/aeso_aci.erl
index 24c6f49..5a1a509 100644
--- a/src/aeso_aci.erl
+++ b/src/aeso_aci.erl
@@ -21,6 +21,8 @@
         , json_encode_expr/1
         , json_encode_type/1]).
 
+-include("aeso_utils.hrl").
+
 -type aci_type()  :: json | string.
 -type json()      :: jsx:json_term().
 -type json_text() :: binary().
@@ -68,9 +70,7 @@ do_contract_interface(Type, Contract, Options) when is_binary(Contract) ->
 do_contract_interface(Type, ContractString, Options) ->
     try
         Ast = aeso_compiler:parse(ContractString, Options),
-        %% io:format("~p\n", [Ast]),
         {TypedAst, _} = aeso_ast_infer_types:infer(Ast, [dont_unfold | Options]),
-        %% io:format("~p\n", [TypedAst]),
         from_typed_ast(Type, TypedAst)
     catch
         throw:{error, Errors} -> {error, Errors}
@@ -83,7 +83,7 @@ from_typed_ast(Type, TypedAst) ->
         string -> do_render_aci_json(JArray)
     end.
 
-encode_contract(Contract = {contract, _, {con, _, Name}, _}) ->
+encode_contract(Contract = {Head, _, {con, _, Name}, _}) when ?IS_CONTRACT_HEAD(Head) ->
     C0 = #{name => encode_name(Name)},
 
     Tdefs0 = [ encode_typedef(T) || T <- sort_decls(contract_types(Contract)) ],
@@ -107,7 +107,7 @@ encode_contract(Contract = {contract, _, {con, _, Name}, _}) ->
                || F <- sort_decls(contract_funcs(Contract)),
                   is_entrypoint(F) ],
 
-    #{contract => C3#{functions => Fdefs, payable => is_payable(Contract)}};
+    #{contract => C3#{kind => Head, functions => Fdefs, payable => is_payable(Contract)}};
 encode_contract(Namespace = {namespace, _, {con, _, Name}, _}) ->
     Tdefs = [ encode_typedef(T) || T <- sort_decls(contract_types(Namespace)) ],
     #{namespace => #{name => encode_name(Name),
@@ -232,13 +232,19 @@ do_render_aci_json(Json) ->
     {ok, list_to_binary(string:join(DecodedContracts, "\n"))}.
 
 decode_contract(#{contract := #{name := Name,
+                                kind := Kind,
                                 payable := Payable,
                                 type_defs := Ts0,
                                 functions := Fs} = C}) ->
     MkTDef = fun(N, T) -> #{name => N, vars => [], typedef => T} end,
     Ts = [ MkTDef(<<"state">>, maps:get(state, C)) || maps:is_key(state, C) ] ++
          [ MkTDef(<<"event">>, maps:get(event, C)) || maps:is_key(event, C) ] ++ Ts0,
-    [payable(Payable), "contract ", io_lib:format("~s", [Name])," =\n",
+    [payable(Payable), case Kind of
+                           contract_main -> "main contract ";
+                           contract_child -> "contract ";
+                           contract_interface -> "contract interface "
+                       end,
+     io_lib:format("~s", [Name])," =\n",
      decode_tdefs(Ts), decode_funcs(Fs)];
 decode_contract(#{namespace := #{name := Name, type_defs := Ts}}) when Ts /= [] ->
     ["namespace ", io_lib:format("~s", [Name])," =\n",
@@ -332,10 +338,10 @@ payable(false) -> "".
 
 %% #contract{Ann, Con, [Declarations]}.
 
-contract_funcs({C, _, _, Decls}) when C == contract; C == namespace ->
+contract_funcs({C, _, _, Decls}) when ?IS_CONTRACT_HEAD(C); C == namespace ->
     [ D || D <- Decls, is_fun(D)].
 
-contract_types({C, _, _, Decls}) when C == contract; C == namespace ->
+contract_types({C, _, _, Decls}) when ?IS_CONTRACT_HEAD(C); C == namespace ->
     [ D || D <- Decls, is_type(D) ].
 
 is_fun({letfun, _, _, _, _, _}) -> true;
diff --git a/src/aeso_ast_infer_types.erl b/src/aeso_ast_infer_types.erl
index 8755cb1..3f8c3ce 100644
--- a/src/aeso_ast_infer_types.erl
+++ b/src/aeso_ast_infer_types.erl
@@ -18,6 +18,8 @@
         , pp_type/2
         ]).
 
+-include("aeso_utils.hrl").
+
 -type utype() :: {fun_t, aeso_syntax:ann(), named_args_t(), [utype()], utype()}
                | {app_t, aeso_syntax:ann(), utype(), [utype()]}
                | {tuple_t, aeso_syntax:ann(), [utype()]}
@@ -123,7 +125,7 @@
     , in_pattern = false              :: boolean()
     , stateful   = false              :: boolean()
     , current_function = none         :: none | aeso_syntax:id()
-    , what       = top                :: top | namespace | contract | main_contract
+    , what       = top                :: top | namespace | contract | contract_interface
     }).
 
 -type env() :: #env{}.
@@ -191,9 +193,9 @@ bind_fun(X, Type, Env) ->
 force_bind_fun(X, Type, Env = #env{ what = What }) ->
     Ann    = aeso_syntax:get_ann(Type),
     NoCode = get_option(no_code, false),
-    Entry = if X == "init", What == main_contract, not NoCode ->
+    Entry = if X == "init", What == contract, not NoCode ->
                     {reserved_init, Ann, Type};
-               What == contract -> {contract_fun, Ann, Type};
+               What == contract_interface -> {contract_fun, Ann, Type};
                true -> {Ann, Type}
             end,
     on_current_scope(Env, fun(Scope = #scope{ funs = Funs }) ->
@@ -261,13 +263,21 @@ contract_call_type({fun_t, Ann, [], Args, Ret}) ->
      Args, {if_t, Ann, Id("protected"), {app_t, Ann, {id, Ann, "option"}, [Ret]}, Ret}}.
 
 -spec bind_contract(aeso_syntax:decl(), env()) -> env().
-bind_contract({contract, Ann, Id, Contents}, Env) ->
+bind_contract({Contract, Ann, Id, Contents}, Env)
+  when ?IS_CONTRACT_HEAD(Contract) ->
     Key    = name(Id),
     Sys    = [{origin, system}],
-    Fields = [ {field_t, AnnF, Entrypoint, contract_call_type(Type)}
-                || {fun_decl, AnnF, Entrypoint, Type} <- Contents ] ++
-              %% Predefined fields
-             [ {field_t, Sys, {id, Sys, "address"}, {id, Sys, "address"}} ],
+    Fields =
+        [ {field_t, AnnF, Entrypoint, contract_call_type(Type)}
+          || {fun_decl, AnnF, Entrypoint, Type} <- Contents ] ++
+        [ {field_t, AnnF, Entrypoint,
+           contract_call_type(
+             {fun_t, AnnF, [], [ArgT || ArgT <- if is_list(Args) -> Args; true -> [Args] end], RetT})
+          }
+          || {letfun, AnnF, Entrypoint, _Named, Args, {typed, _, _, RetT}} <- Contents
+        ] ++
+        %% Predefined fields
+        [ {field_t, Sys, {id, Sys, "address"}, {id, Sys, "address"}} ],
     FieldInfo = [ {Entrypoint, #field_info{ ann      = FieldAnn,
                                             kind     = contract,
                                             field_t  = Type,
@@ -463,6 +473,7 @@ global_env() ->
                      {"block_height", Int},
                      {"difficulty",   Int},
                      {"gas_limit",    Int},
+                     {"bytecode_hash", Fun1(Address, Option(Hash))},
                      %% Tx constructors
                      {"GAMetaTx",     Fun([Address, Int], GAMetaTx)},
                      {"PayingForTx",  Fun([Address, Int], PayForTx)},
@@ -701,7 +712,10 @@ infer(Contracts, Options) ->
         create_options(Options),
         ets_new(type_vars, [set]),
         check_modifiers(Env, Contracts),
-        {Env1, Decls} = infer1(Env, Contracts, [], Options),
+        create_type_errors(),
+        Contracts1 = identify_main_contract(Contracts),
+        destroy_and_report_type_errors(Env),
+        {Env1, Decls} = infer1(Env, Contracts1, [], Options),
         {Env2, DeclsFolded, DeclsUnfolded} =
             case proplists:get_value(dont_unfold, Options, false) of
                 true  -> {Env1, Decls, Decls};
@@ -719,12 +733,16 @@ infer(Contracts, Options) ->
 -spec infer1(env(), [aeso_syntax:decl()], [aeso_syntax:decl()], list(option())) ->
     {env(), [aeso_syntax:decl()]}.
 infer1(Env, [], Acc, _Options) -> {Env, lists:reverse(Acc)};
-infer1(Env, [{contract, Ann, ConName, Code} | Rest], Acc, Options) ->
+infer1(Env, [{Contract, Ann, ConName, Code} | Rest], Acc, Options)
+  when ?IS_CONTRACT_HEAD(Contract) ->
     %% do type inference on each contract independently.
     check_scope_name_clash(Env, contract, ConName),
-    What = if Rest == [] -> main_contract; true -> contract end,
+    What = case aeso_syntax:get_ann(interface, Ann, false) of
+               true -> contract_interface;
+               false -> contract
+           end,
     {Env1, Code1} = infer_contract_top(push_scope(contract, ConName, Env), What, Code, Options),
-    Contract1 = {contract, Ann, ConName, Code1},
+    Contract1 = {Contract, Ann, ConName, Code1},
     Env2 = pop_scope(Env1),
     Env3 = bind_contract(Contract1, Env2),
     infer1(Env3, Rest, [Contract1 | Acc], Options);
@@ -737,6 +755,26 @@ infer1(Env, [{pragma, _, _} | Rest], Acc, Options) ->
     %% Pragmas are checked in check_modifiers
     infer1(Env, Rest, Acc, Options).
 
+%% Checks if the main contract is somehow defined.
+%% Performs some basic sorting to make the dependencies more happy.
+identify_main_contract(Contracts) ->
+    Childs     = [C || C = {contract_child, _, _, _} <- Contracts],
+    Mains      = [C || C = {contract_main, _, _, _} <- Contracts],
+    Interfaces = [C || C = {contract_interface, _, _, _} <- Contracts],
+    Namespaces = [N || N = {namespace, _, _, _} <- Contracts],
+    case Mains of
+        [] -> case Childs of
+                  [] -> type_error({main_contract_undefined});
+                  [{contract_child, Ann, Con, Body}] ->
+                      Interfaces ++ Namespaces ++
+                          [C || C = {_, _, Con1, _} <- Childs, Con1 /= Con] ++
+                          [{contract_main, Ann, Con, Body}];
+                  _ -> type_error({ambiguous_main_contract})
+              end;
+        [_] -> Interfaces ++ Namespaces ++ Childs ++ Mains;
+        _ -> type_error({multiple_main_contracts})
+    end.
+
 check_scope_name_clash(Env, Kind, Name) ->
     case get_scope(Env, qname(Name)) of
         false -> ok;
@@ -746,7 +784,7 @@ check_scope_name_clash(Env, Kind, Name) ->
             destroy_and_report_type_errors(Env)
     end.
 
--spec infer_contract_top(env(), main_contract | contract | namespace, [aeso_syntax:decl()], list(option())) ->
+-spec infer_contract_top(env(), contract_interface | contract | namespace, [aeso_syntax:decl()], list(option())) ->
     {env(), [aeso_syntax:decl()]}.
 infer_contract_top(Env, Kind, Defs0, Options) ->
     create_type_errors(),
@@ -756,7 +794,7 @@ infer_contract_top(Env, Kind, Defs0, Options) ->
 
 %% infer_contract takes a proplist mapping global names to types, and
 %% a list of definitions.
--spec infer_contract(env(), main_contract | contract | namespace, [aeso_syntax:decl()], list(option())) -> {env(), [aeso_syntax:decl()]}.
+-spec infer_contract(env(), contract_interface | contract | namespace, [aeso_syntax:decl()], list(option())) -> {env(), [aeso_syntax:decl()]}.
 infer_contract(Env0, What, Defs0, Options) ->
     create_type_errors(),
     Defs01 = process_blocks(Defs0),
@@ -772,19 +810,19 @@ infer_contract(Env0, What, Defs0, Options) ->
               ({fun_decl, _, _, _})       -> prototype;
               (_)                         -> unexpected
            end,
-    Get = fun(K) -> [ Def || Def <- Defs, Kind(Def) == K ] end,
-    {Env1, TypeDefs} = check_typedefs(Env, Get(type)),
+    Get = fun(K, In) -> [ Def || Def <- In, Kind(Def) == K ] end,
+    {Env1, TypeDefs} = check_typedefs(Env, Get(type, Defs)),
     create_type_errors(),
-    check_unexpected(Get(unexpected)),
+    check_unexpected(Get(unexpected, Defs)),
     Env2 =
         case What of
-            namespace     -> Env1;
-            contract      -> Env1;
-            main_contract -> bind_state(Env1)   %% bind state and put
+            namespace          -> Env1;
+            contract_interface -> Env1;
+            contract           -> bind_state(Env1)   %% bind state and put
         end,
-    {ProtoSigs, Decls} = lists:unzip([ check_fundecl(Env1, Decl) || Decl <- Get(prototype) ]),
+    {ProtoSigs, Decls} = lists:unzip([ check_fundecl(Env1, Decl) || Decl <- Get(prototype, Defs) ]),
     Env3      = bind_funs(ProtoSigs, Env2),
-    Functions = Get(function),
+    Functions = Get(function, Defs),
     %% Check for duplicates in Functions (we turn it into a map below)
     FunBind   = fun({letfun, Ann, {id, _, Fun}, _, _, _})   -> {Fun, {tuple_t, Ann, []}};
                    ({fun_clauses, Ann, {id, _, Fun}, _, _}) -> {Fun, {tuple_t, Ann, []}} end,
@@ -794,11 +832,11 @@ infer_contract(Env0, What, Defs0, Options) ->
     check_reserved_entrypoints(FunMap),
     DepGraph  = maps:map(fun(_, Def) -> aeso_syntax_utils:used_ids(Def) end, FunMap),
     SCCs      = aeso_utils:scc(DepGraph),
-    %% io:format("Dependency sorted functions:\n  ~p\n", [SCCs]),
     {Env4, Defs1} = check_sccs(Env3, FunMap, SCCs, []),
     %% Check that `init` doesn't read or write the state
     check_state_dependencies(Env4, Defs1),
     destroy_and_report_type_errors(Env4),
+    %% Add inferred types of definitions
     {Env4, TypeDefs ++ Decls ++ Defs1}.
 
 %% Restructure blocks into multi-clause fundefs (`fun_clauses`).
@@ -830,9 +868,9 @@ expose_internals(Defs, What) ->
     [ begin
           Ann = element(2, Def),
           NewAnn = case What of
-                       namespace -> [A ||A <- Ann, A /= {private, true}, A /= private];
-                       main_contract -> [{entrypoint, true}|Ann];  % minor duplication
-                       contract -> Ann
+                       namespace          -> [A ||A <- Ann, A /= {private, true}, A /= private];
+                       contract           -> [{entrypoint, true}|Ann];  % minor duplication
+                       contract_interface -> Ann
                    end,
           Def1 = setelement(2, Def, NewAnn),
           case Def1 of  % fix inner clauses
@@ -907,15 +945,16 @@ check_modifiers(Env, Contracts) ->
     check_modifiers_(Env, Contracts),
     destroy_and_report_type_errors(Env).
 
-check_modifiers_(Env, [{contract, _, Con, Decls} | Rest]) ->
-    IsMain = Rest == [],
+check_modifiers_(Env, [{Contract, _, Con, Decls} | Rest])
+  when ?IS_CONTRACT_HEAD(Contract) ->
+    IsInterface = Contract =:= contract_interface,
     check_modifiers1(contract, Decls),
     case {lists:keymember(letfun, 1, Decls),
             [ D || D <- Decls, aeso_syntax:get_ann(entrypoint, D, false) ]} of
         {true, []} -> type_error({contract_has_no_entrypoints, Con});
-        _ when not IsMain ->
-            case [ {Ann, Id} || {letfun, Ann, Id, _, _, _} <- Decls ] of
-                [{Ann, Id} | _] -> type_error({definition_in_non_main_contract, Ann, Id});
+        _ when IsInterface ->
+            case [ {AnnF, Id} || {letfun, AnnF, Id, _, _, _} <- Decls ] of
+                [{AnnF, Id} | _] -> type_error({definition_in_contract_interface, AnnF, Id});
                 [] -> ok
             end;
         _ -> ok
@@ -2653,7 +2692,7 @@ mk_error({namespace, _Pos, {con, Pos, Name}, _Def}) ->
     Msg = io_lib:format("Nested namespaces are not allowed\nNamespace '~s' at ~s not defined at top level.\n",
                         [Name, pp_loc(Pos)]),
     mk_t_err(pos(Pos), Msg);
-mk_error({contract, _Pos, {con, Pos, Name}, _Def}) ->
+mk_error({Contract, _Pos, {con, Pos, Name}, _Def}) when ?IS_CONTRACT_HEAD(Contract) ->
     Msg = io_lib:format("Nested contracts are not allowed\nContract '~s' at ~s not defined at top level.\n",
                         [Name, pp_loc(Pos)]),
     mk_t_err(pos(Pos), Msg);
@@ -2728,8 +2767,8 @@ mk_error({contract_has_no_entrypoints, Con}) ->
                         "contract functions must be declared with the 'entrypoint' keyword instead of\n"
                         "'function'.\n", [pp_expr("", Con), pp_loc(Con)]),
     mk_t_err(pos(Con), Msg);
-mk_error({definition_in_non_main_contract, Ann, {id, _, Id}}) ->
-    Msg = "Only the main contract can contain defined functions or entrypoints.\n",
+mk_error({definition_in_contract_interface, Ann, {id, _, Id}}) ->
+    Msg = "Contract interfaces cannot contain defined functions or entrypoints.\n",
     Cxt = io_lib:format("Fix: replace the definition of '~s' by a type signature.\n", [Id]),
     mk_t_err(pos(Ann), Msg, Cxt);
 mk_error({unbound_type, Type}) ->
@@ -2798,6 +2837,15 @@ mk_error({named_argument_must_be_literal_bool, Name, Arg}) ->
 mk_error({conflicting_updates_for_field, Upd, Key}) ->
     Msg = io_lib:format("Conflicting updates for field '~s'\n", [Key]),
     mk_t_err(pos(Upd), Msg);
+mk_error({ambiguous_main_contract}) ->
+    Msg = "Could not deduce the main contract. You can point it manually with `main` keyword.",
+    mk_t_err(pos(0, 0), Msg);
+mk_error({main_contract_undefined}) ->
+    Msg = "No contract defined.",
+    mk_t_err(pos(0, 0), Msg);
+mk_error({multiple_main_contracts}) ->
+    Msg = "Up to one main contract can be defined.",
+    mk_t_err(pos(0, 0), Msg);
 mk_error(Err) ->
     Msg = io_lib:format("Unknown error: ~p\n", [Err]),
     mk_t_err(pos(0, 0), Msg).
diff --git a/src/aeso_ast_to_fcode.erl b/src/aeso_ast_to_fcode.erl
index 07f4e01..27de5b3 100644
--- a/src/aeso_ast_to_fcode.erl
+++ b/src/aeso_ast_to_fcode.erl
@@ -12,6 +12,8 @@
 -export([ast_to_fcode/2, format_fexpr/1]).
 -export_type([fcode/0, fexpr/0, fun_def/0]).
 
+-include("aeso_utils.hrl").
+
 %% -- Type definitions -------------------------------------------------------
 
 -type option() :: term().
@@ -136,6 +138,7 @@
 -type type_env() :: #{ sophia_name() => type_def() }.
 -type fun_env()  :: #{ sophia_name() => {fun_name(), non_neg_integer()} }.
 -type con_env()  :: #{ sophia_name() => con_tag() }.
+-type child_con_env() :: #{sophia_name() => fcode()}.
 -type builtins() :: #{ sophia_name() => {builtin(), non_neg_integer() | none} }.
 
 -type context() :: {main_contract, string()}
@@ -144,16 +147,17 @@
 
 -type state_layout() :: {tuple, [state_layout()]} | {reg, state_reg()}.
 
--type env() :: #{ type_env     := type_env(),
-                  fun_env      := fun_env(),
-                  con_env      := con_env(),
-                  event_type   => aeso_syntax:typedef(),
-                  builtins     := builtins(),
-                  options      := [option()],
-                  state_layout => state_layout(),
-                  context      => context(),
-                  vars         => [var_name()],
-                  functions    := #{ fun_name() => fun_def() } }.
+-type env() :: #{ type_env      := type_env(),
+                  fun_env       := fun_env(),
+                  con_env       := con_env(),
+                  child_con_env := child_con_env(),
+                  event_type    => aeso_syntax:typedef(),
+                  builtins      := builtins(),
+                  options       := [option()],
+                  state_layout  => state_layout(),
+                  context       => context(),
+                  vars          => [var_name()],
+                  functions     := #{ fun_name() => fun_def() } }.
 
 -define(HASH_BYTES, 32).
 
@@ -182,6 +186,7 @@ init_env(Options) ->
     #{ type_env  => init_type_env(),
        fun_env   => #{},
        builtins  => builtins(),
+       child_con_env => #{},
        con_env   => #{["None"]        => #con_tag{ tag = 0, arities = [0, 1] },
                       ["Some"]        => #con_tag{ tag = 1, arities = [0, 1] },
                       ["RelativeTTL"] => #con_tag{ tag = 0, arities = [1, 1] },
@@ -308,30 +313,41 @@ get_option(Opt, Env, Default) ->
 %% -- Compilation ------------------------------------------------------------
 
 -spec to_fcode(env(), aeso_syntax:ast()) -> fcode().
-to_fcode(Env, [{contract, Attrs, MainCon = {con, _, Main}, Decls}]) ->
-    #{ builtins := Builtins } = Env,
-    MainEnv = Env#{ context  => {main_contract, Main},
-                    builtins => Builtins#{[Main, "state"]          => {get_state, none},
-                                          [Main, "put"]            => {set_state, 1},
-                                          [Main, "Chain", "event"] => {chain_event, 1}} },
-    #{ functions := Funs } = Env1 =
-        decls_to_fcode(MainEnv, Decls),
-    StateType   = lookup_type(Env1, [Main, "state"], [], {tuple, []}),
-    EventType   = lookup_type(Env1, [Main, "event"], [], none),
-    StateLayout = state_layout(Env1),
-    Payable     = proplists:get_value(payable, Attrs, false),
-    #{ contract_name => Main,
-       state_type    => StateType,
-       state_layout  => StateLayout,
-       event_type    => EventType,
-       payable       => Payable,
-       functions     => add_init_function(Env1, MainCon, StateType,
-                        add_event_function(Env1, EventType, Funs)) };
-to_fcode(_Env, [NotContract]) ->
-    fcode_error({last_declaration_must_be_contract, NotContract});
-to_fcode(Env, [{contract, _, {con, _, Con}, Decls} | Code]) ->
-    Env1 = decls_to_fcode(Env#{ context => {abstract_contract, Con} }, Decls),
-    to_fcode(Env1, Code);
+to_fcode(Env, [{Contract, Attrs, Con = {con, _, Name}, Decls}|Rest])
+  when ?IS_CONTRACT_HEAD(Contract) ->
+    case Contract =:= contract_interface of
+        false ->
+
+            #{ builtins := Builtins } = Env,
+            ConEnv = Env#{ context  => {main_contract, Name},
+                           builtins => Builtins#{[Name, "state"]          => {get_state, none},
+                                                 [Name, "put"]            => {set_state, 1},
+                                                 [Name, "Chain", "event"] => {chain_event, 1}} },
+            #{ functions := Funs } = Env1 =
+                decls_to_fcode(ConEnv, Decls),
+            StateType   = lookup_type(Env1, [Name, "state"], [], {tuple, []}),
+            EventType   = lookup_type(Env1, [Name, "event"], [], none),
+            StateLayout = state_layout(Env1),
+            Payable     = proplists:get_value(payable, Attrs, false),
+            ConFcode = #{ contract_name => Name,
+                          state_type    => StateType,
+                          state_layout  => StateLayout,
+                          event_type    => EventType,
+                          payable       => Payable,
+                          functions     => add_init_function(Env1, Con, StateType,
+                                                             add_event_function(Env1, EventType, Funs)) },
+            case Contract of
+                contract_main -> Rest = [], ConFcode;
+                contract_child ->
+                    Env2 = add_child_con(Env1, Name, ConFcode),
+                    to_fcode(Env2, Rest)
+            end;
+        true ->
+            Env1 = decls_to_fcode(Env#{ context => {abstract_contract, Con} }, Decls),
+            to_fcode(Env1, Rest)
+    end;
+to_fcode(_Env, [NotMain = {NotMainHead, _ ,_ , _}]) when NotMainHead =/= main_contract ->
+    fcode_error({last_declaration_must_be_main_contract, NotMain});
 to_fcode(Env, [{namespace, _, {con, _, Con}, Decls} | Code]) ->
     Env1 = decls_to_fcode(Env#{ context => {namespace, Con} }, Decls),
     to_fcode(Env1, Code).
@@ -341,9 +357,7 @@ decls_to_fcode(Env, Decls) ->
     %% First compute mapping from Sophia names to fun_names and add it to the
     %% environment.
     Env1 = add_fun_env(Env, Decls),
-    lists:foldl(fun(D, E) ->
-                    R = decl_to_fcode(E, D),
-                    R
+    lists:foldl(fun(D, E) -> decl_to_fcode(E, D)
                 end, Env1, Decls).
 
 -spec decl_to_fcode(env(), aeso_syntax:decl()) -> env().
@@ -1614,6 +1628,10 @@ bind_constructors(Env = #{ con_env := ConEnv }, NewCons) ->
 
 %% -- Names --
 
+-spec add_child_con(env(), sophia_name(), fcode()) -> env().
+add_child_con(Env = #{child_con_env := CEnv}, Name, Fcode) ->
+    Env#{ child_con_env := CEnv#{Name => Fcode} }.
+
 -spec add_fun_env(env(), [aeso_syntax:decl()]) -> env().
 add_fun_env(Env = #{ context := {abstract_contract, _} }, _) -> Env;  %% no functions from abstract contracts
 add_fun_env(Env = #{ fun_env := FunEnv }, Decls) ->
diff --git a/src/aeso_ast_to_icode.erl b/src/aeso_ast_to_icode.erl
index b1a1874..8cace86 100644
--- a/src/aeso_ast_to_icode.erl
+++ b/src/aeso_ast_to_icode.erl
@@ -14,12 +14,13 @@
 
 -include_lib("aebytecode/include/aeb_opcodes.hrl").
 -include("aeso_icode.hrl").
+-include("aeso_utils.hrl").
 
 -spec convert_typed(aeso_syntax:ast(), list()) -> aeso_icode:icode().
 convert_typed(TypedTree, Options) ->
     {Payable, Name} =
         case lists:last(TypedTree) of
-            {contract, Attrs, {con, _, Con}, _} ->
+            {Contr, Attrs, {con, _, Con}, _} when ?IS_CONTRACT_HEAD(Contr) ->
                 {proplists:get_value(payable, Attrs, false), Con};
             Decl ->
                 gen_error({last_declaration_must_be_contract, Decl})
@@ -29,7 +30,8 @@ convert_typed(TypedTree, Options) ->
     Icode    = code(TypedTree, NewIcode, Options),
     deadcode_elimination(Icode).
 
-code([{contract, _Attribs, Con, Code}|Rest], Icode, Options) ->
+code([{Contract, _Attribs, Con, Code}|Rest], Icode, Options)
+  when ?IS_CONTRACT_HEAD(Contract) ->
     NewIcode = contract_to_icode(Code, aeso_icode:set_namespace(Con, Icode)),
     code(Rest, NewIcode, Options);
 code([{namespace, _Ann, Name, Code}|Rest], Icode, Options) ->
diff --git a/src/aeso_code_errors.erl b/src/aeso_code_errors.erl
index 05bc135..bb2568d 100644
--- a/src/aeso_code_errors.erl
+++ b/src/aeso_code_errors.erl
@@ -10,9 +10,9 @@
 
 -export([format/1, pos/1]).
 
-format({last_declaration_must_be_contract, Decl = {namespace, _, {con, _, C}, _}}) ->
-    Msg = io_lib:format("Expected a contract as the last declaration instead of the namespace '~s'\n",
-                        [C]),
+format({last_declaration_must_be_contract, Decl = {Kind, _, {con, _, C}, _}}) ->
+    Msg = io_lib:format("Expected a contract as the last declaration instead of the ~p '~s'\n",
+                        [Kind, C]),
     mk_err(pos(Decl), Msg);
 format({missing_init_function, Con}) ->
     Msg = io_lib:format("Missing init function for the contract '~s'.\n", [pp_expr(Con)]),
diff --git a/src/aeso_compiler.erl b/src/aeso_compiler.erl
index 25cb1b9..930c70c 100644
--- a/src/aeso_compiler.erl
+++ b/src/aeso_compiler.erl
@@ -28,6 +28,7 @@
 
 -include_lib("aebytecode/include/aeb_opcodes.hrl").
 -include("aeso_icode.hrl").
+-include("aeso_utils.hrl").
 
 
 -type option() :: pp_sophia_code
@@ -468,7 +469,7 @@ error_missing_call_function() ->
     Msg = "Internal error: missing '__call'-function",
     aeso_errors:throw(aeso_errors:new(internal_error, Msg)).
 
-get_call_type([{contract, _, _, Defs}]) ->
+get_call_type([{Contract, _, _, Defs}]) when ?IS_CONTRACT_HEAD(Contract) ->
     case [ {lists:last(QFunName), FunType}
           || {letfun, _, {id, _, ?CALL_NAME}, [], _Ret,
                 {typed, _,
@@ -482,7 +483,7 @@ get_call_type([_ | Contracts]) ->
     get_call_type(Contracts).
 
 -dialyzer({nowarn_function, get_decode_type/2}).
-get_decode_type(FunName, [{contract, Ann, _, Defs}]) ->
+get_decode_type(FunName, [{Contract, Ann, _, Defs}]) when ?IS_CONTRACT_HEAD(Contract) ->
     GetType = fun({letfun, _, {id, _, Name}, Args, Ret, _})               when Name == FunName -> [{Args, Ret}];
                  ({fun_decl, _, {id, _, Name}, {fun_t, _, _, Args, Ret}}) when Name == FunName -> [{Args, Ret}];
                  (_) -> [] end,
diff --git a/src/aeso_parser.erl b/src/aeso_parser.erl
index acb09c6..c29403d 100644
--- a/src/aeso_parser.erl
+++ b/src/aeso_parser.erl
@@ -93,8 +93,20 @@ decl() ->
     ?LAZY_P(
     choice(
       %% Contract declaration
-    [ ?RULE(keyword(contract),  con(), tok('='), maybe_block(decl()), {contract, _1, _2, _4})
-    , ?RULE(token(payable),     keyword(contract), con(), tok('='), maybe_block(decl()), add_modifiers([_1], {contract, _2, _3, _5}))
+    [ ?RULE(token(main), keyword(contract),
+            con(), tok('='), maybe_block(decl()), {contract_main, _2, _3, _5})
+    , ?RULE(keyword(contract),
+            con(), tok('='), maybe_block(decl()), {contract_child, _1, _2, _4})
+    , ?RULE(keyword(contract), token(interface),
+            con(), tok('='), maybe_block(decl()), {contract_interface, _1, _3, _5})
+    , ?RULE(token(payable), token(main), keyword(contract),
+            con(), tok('='), maybe_block(decl()), add_modifiers([_1], {contract_main, _3, _4, _6}))
+    , ?RULE(token(payable), keyword(contract),
+            con(), tok('='), maybe_block(decl()), add_modifiers([_1], {contract_child, _2, _3, _5}))
+    , ?RULE(token(payable), keyword(contract), token(interface),
+            con(), tok('='), maybe_block(decl()), add_modifiers([_1], {contract_interface, _2, _4, _6}))
+
+
     , ?RULE(keyword(namespace), con(), tok('='), maybe_block(decl()), {namespace, _1, _2, _4})
     , ?RULE(keyword(include),   str(), {include, get_ann(_1), _2})
     , pragma()
diff --git a/src/aeso_pretty.erl b/src/aeso_pretty.erl
index dfbd577..6b43b4c 100644
--- a/src/aeso_pretty.erl
+++ b/src/aeso_pretty.erl
@@ -13,6 +13,8 @@
 
 -export_type([options/0]).
 
+-include("aeso_utils.hrl").
+
 -type doc() :: prettypr:document().
 -type options() :: [{indent, non_neg_integer()} | show_generated].
 
@@ -131,6 +133,10 @@ typed(A, Type) ->
         false -> follow(hsep(A, text(":")), type(Type))
     end.
 
+contract_head(contract_main)      -> text("main contract");
+contract_head(contract_child)     -> text("contract");
+contract_head(contract_interface) -> text("contract interface").
+
 %% -- Exports ----------------------------------------------------------------
 
 -spec decls([aeso_syntax:decl()], options()) -> doc().
@@ -145,11 +151,11 @@ decl(D, Options) ->
     with_options(Options, fun() -> decl(D) end).
 
 -spec decl(aeso_syntax:decl()) -> doc().
-decl({contract, Attrs, C, Ds}) ->
+decl({Con, Attrs, C, Ds}) when ?IS_CONTRACT_HEAD(Con) ->
     Mod = fun({Mod, true}) when Mod == payable ->
                   text(atom_to_list(Mod));
              (_) -> empty() end,
-    block(follow( hsep(lists:map(Mod, Attrs) ++ [text("contract")])
+    block(follow( hsep(lists:map(Mod, Attrs) ++ [contract_head(Con)])
                 , hsep(name(C), text("="))), decls(Ds));
 decl({namespace, _, C, Ds}) ->
     block(follow(text("namespace"), hsep(name(C), text("="))), decls(Ds));
diff --git a/src/aeso_scan.erl b/src/aeso_scan.erl
index e81757f..2c5d301 100644
--- a/src/aeso_scan.erl
+++ b/src/aeso_scan.erl
@@ -44,7 +44,9 @@ lexer() ->
         , {"[^/*]+|[/*]", skip()} ],
 
     Keywords = ["contract", "include", "let", "switch", "type", "record", "datatype", "if", "elif", "else", "function",
-                "stateful", "payable", "true", "false", "mod", "public", "entrypoint", "private", "indexed", "namespace"],
+                "stateful", "payable", "true", "false", "mod", "public", "entrypoint", "private", "indexed", "namespace",
+                "interface", "main"
+               ],
     KW = string:join(Keywords, "|"),
 
     Rules =
diff --git a/src/aeso_syntax.erl b/src/aeso_syntax.erl
index 1d01ef0..b48e4ff 100644
--- a/src/aeso_syntax.erl
+++ b/src/aeso_syntax.erl
@@ -25,7 +25,8 @@
 -type ann_origin() :: system | user.
 -type ann_format() :: '?:' | hex | infix | prefix | elif.
 
--type ann() :: [{line, ann_line()} | {col, ann_col()} | {format, ann_format()} | {origin, ann_origin()} | stateful | private].
+-type ann() :: [ {line, ann_line()} | {col, ann_col()} | {format, ann_format()} | {origin, ann_origin()}
+               | stateful | private] | payable | main | interface.
 
 -type name() :: string().
 -type id()   :: {id,   ann(), name()}.
@@ -34,7 +35,9 @@
 -type qcon() :: {qcon, ann(), [name()]}.
 -type tvar() :: {tvar, ann(), name()}.
 
--type decl() :: {contract, ann(), con(), [decl()]}
+-type decl() :: {contract_main, ann(), con(), [decl()]}
+              | {contract_child, ann(), con(), [decl()]}
+              | {contract_interface, ann(), con(), [decl()]}
               | {namespace, ann(), con(), [decl()]}
               | {pragma, ann(), pragma()}
               | {type_decl, ann(), id(), [tvar()]} % Only for error msgs
diff --git a/test/aeso_abi_tests.erl b/test/aeso_abi_tests.erl
index 6f1fb02..9306657 100644
--- a/test/aeso_abi_tests.erl
+++ b/test/aeso_abi_tests.erl
@@ -190,7 +190,7 @@ parameterized_contract(ExtraCode, FunName, Types) ->
     lists:flatten(
         ["contract Remote =\n"
          "  entrypoint bla : () => unit\n\n"
-         "contract Dummy =\n",
+         "main contract Dummy =\n",
          ExtraCode, "\n",
          "  type an_alias('a) = string * 'a\n"
          "  record r = {x : an_alias(int), y : variant}\n"
diff --git a/test/aeso_calldata_tests.erl b/test/aeso_calldata_tests.erl
index c939893..58d66e3 100644
--- a/test/aeso_calldata_tests.erl
+++ b/test/aeso_calldata_tests.erl
@@ -59,8 +59,8 @@ calldata_aci_test_() ->
         end} || {ContractName, Fun, Args} <- compilable_contracts()].
 
 parse_args(Fun, Args) ->
-    [{contract, _, _, [{letfun, _, _, _, _, {app, _, _, AST}}]}] =
-        aeso_parser:string("contract Temp = function foo() = " ++ Fun ++ "(" ++ string:join(Args, ", ") ++ ")"),
+    [{contract_main, _, _, [{letfun, _, _, _, _, {app, _, _, AST}}]}] =
+        aeso_parser:string("main contract Temp = function foo() = " ++ Fun ++ "(" ++ string:join(Args, ", ") ++ ")"),
     strip_ann(AST).
 
 strip_ann(T) when is_tuple(T) ->
diff --git a/test/aeso_compiler_tests.erl b/test/aeso_compiler_tests.erl
index 36e70b4..3e3cfa5 100644
--- a/test/aeso_compiler_tests.erl
+++ b/test/aeso_compiler_tests.erl
@@ -179,17 +179,12 @@ compilable_contracts() ->
      "lhs_matching",
      "more_strings",
      "protected_call",
-     "hermetization_turnoff"
+     "hermetization_turnoff",
+     "multiple_contracts"
     ].
 
 not_compilable_on(fate) -> [];
-not_compilable_on(aevm) ->
-    [ "stdlib_include", "manual_stdlib_include", "pairing_crypto"
-    , "aens_update", "basic_auth_tx", "more_strings"
-    , "unapplied_builtins", "bytes_to_x", "state_handling", "protected_call"
-    , "hermetization_turnoff"
-
-    ].
+not_compilable_on(aevm) -> compilable_contracts().
 
 debug_mode_contracts() ->
     ["hermetization_turnoff"].
@@ -635,9 +630,9 @@ failing_contracts() ->
          <<?Pos(2, 1)
            "Cannot compile with this version of the compiler,\n"
            "because it does not satisfy the constraint ", Version/binary, " == 9.9.9">>])
-    , ?TYPE_ERROR(multiple_contracts,
+    , ?TYPE_ERROR(interface_with_defs,
          [<<?Pos(2, 3)
-            "Only the main contract can contain defined functions or entrypoints.\n"
+            "Contract interfaces cannot contain defined functions or entrypoints.\n"
             "Fix: replace the definition of 'foo' by a type signature.">>])
     , ?TYPE_ERROR(contract_as_namespace,
          [<<?Pos(5, 28)
@@ -746,9 +741,7 @@ failing_contracts() ->
                        {fate, ?Msg(File, Line, Col, ErrFATE)}]}).
 
 failing_code_gen_contracts() ->
-    [ ?SAME(last_declaration_must_be_contract, 1, 1,
-            "Expected a contract as the last declaration instead of the namespace 'LastDeclarationIsNotAContract'")
-    , ?SAME(missing_definition, 2, 14,
+    [ ?SAME(missing_definition, 2, 14,
             "Missing definition of function 'foo'.")
     , ?AEVM(polymorphic_entrypoint, 2, 17,
             "The argument\n"
diff --git a/test/aeso_parser_tests.erl b/test/aeso_parser_tests.erl
index c978b0a..f8e2eee 100644
--- a/test/aeso_parser_tests.erl
+++ b/test/aeso_parser_tests.erl
@@ -12,10 +12,10 @@ simple_contracts_test_() ->
      fun(_) -> ok end,
      [{"Parse a contract with an identity function.",
        fun() ->
-            Text = "contract Identity =\n"
+            Text = "main contract Identity =\n"
                    "  function id(x) = x\n",
             ?assertMatch(
-                [{contract, _, {con, _, "Identity"},
+                [{contract_main, _, {con, _, "Identity"},
                     [{letfun, _, {id, _, "id"}, [{id, _, "x"}], {id, _, "_"},
                         {id, _, "x"}}]}], parse_string(Text)),
             ok
diff --git a/test/contracts/__call.aes b/test/contracts/__call.aes
index 1e19b5b..1f90e04 100644
--- a/test/contracts/__call.aes
+++ b/test/contracts/__call.aes
@@ -1,5 +1,5 @@
 
 contract Identity =
-  function main (x:int) = x
+  function main_fun (x:int) = x
 
   function __call() = 12
diff --git a/test/contracts/address_chain.aes b/test/contracts/address_chain.aes
index 4c55a45..da5a111 100644
--- a/test/contracts/address_chain.aes
+++ b/test/contracts/address_chain.aes
@@ -1,5 +1,5 @@
-contract Remote =
-  entrypoint main : (int) => unit
+contract interface Remote =
+  entrypoint main_fun : (int) => unit
 
 contract AddrChain =
   type o_type = oracle(string, map(string, int))
diff --git a/test/contracts/address_literals.aes b/test/contracts/address_literals.aes
index 15007cf..94e7e0c 100644
--- a/test/contracts/address_literals.aes
+++ b/test/contracts/address_literals.aes
@@ -1,5 +1,5 @@
 
-contract Remote =
+contract interface Remote =
   entrypoint foo : () => unit
 
 contract AddressLiterals =
diff --git a/test/contracts/bad_address_literals.aes b/test/contracts/bad_address_literals.aes
index 1750846..30eebac 100644
--- a/test/contracts/bad_address_literals.aes
+++ b/test/contracts/bad_address_literals.aes
@@ -1,5 +1,5 @@
 
-contract Remote =
+contract interface Remote =
   entrypoint foo : () => unit
 
 contract AddressLiterals =
diff --git a/test/contracts/bad_protected_call.aes b/test/contracts/bad_protected_call.aes
index ba1f59c..9b7cf9d 100644
--- a/test/contracts/bad_protected_call.aes
+++ b/test/contracts/bad_protected_call.aes
@@ -1,4 +1,4 @@
-contract Remote =
+contract interface Remote =
   entrypoint id : int => int
 
 contract ProtectedCall =
diff --git a/test/contracts/bad_top_level_decl.aes b/test/contracts/bad_top_level_decl.aes
index 5475fb6..e9053aa 100644
--- a/test/contracts/bad_top_level_decl.aes
+++ b/test/contracts/bad_top_level_decl.aes
@@ -1,3 +1,3 @@
 function square(x) = x ^ 2
 contract Main =
-  entrypoint main() = square(10)
+  entrypoint main_fun() = square(10)
diff --git a/test/contracts/code_errors/bad_aens_resolve.aes b/test/contracts/code_errors/bad_aens_resolve.aes
index 38d932b..8700dfb 100644
--- a/test/contracts/code_errors/bad_aens_resolve.aes
+++ b/test/contracts/code_errors/bad_aens_resolve.aes
@@ -5,5 +5,5 @@ contract BadAENSresolve =
   function fail() : t(int) =
     AENS.resolve("foo.aet", "whatever")
 
-  entrypoint main() = ()
+  entrypoint main_fun() = ()
 
diff --git a/test/contracts/code_errors/higher_order_map_keys.aes b/test/contracts/code_errors/higher_order_map_keys.aes
index a5fa742..98327e2 100644
--- a/test/contracts/code_errors/higher_order_map_keys.aes
+++ b/test/contracts/code_errors/higher_order_map_keys.aes
@@ -3,4 +3,4 @@ contract MapAsMapKey =
 
   function foo(m) : t(int => int) = {[m] = 0}
 
-  entrypoint main() = ()
+  entrypoint main_fun() = ()
diff --git a/test/contracts/code_errors/higher_order_query_type.aes b/test/contracts/code_errors/higher_order_query_type.aes
index 39d533f..1f4a4e6 100644
--- a/test/contracts/code_errors/higher_order_query_type.aes
+++ b/test/contracts/code_errors/higher_order_query_type.aes
@@ -2,4 +2,4 @@ contract HigherOrderQueryType =
   stateful function foo(o) : oracle_query(_, string ) =
     Oracle.query(o, (x) => x + 1, 100, RelativeTTL(100), RelativeTTL(100))
 
-  entrypoint main() = ()
+  entrypoint main_fun() = ()
diff --git a/test/contracts/code_errors/higher_order_response_type.aes b/test/contracts/code_errors/higher_order_response_type.aes
index ae4ec93..87da03c 100644
--- a/test/contracts/code_errors/higher_order_response_type.aes
+++ b/test/contracts/code_errors/higher_order_response_type.aes
@@ -2,4 +2,4 @@ contract HigherOrderResponseType =
   stateful function foo(o, q : oracle_query(string, _)) =
     Oracle.respond(o, q, (x) => x + 1)
 
-  entrypoint main() = ()
+  entrypoint main_fun() = ()
diff --git a/test/contracts/code_errors/last_declaration_must_be_contract.aes b/test/contracts/code_errors/last_declaration_must_be_contract.aes
deleted file mode 100644
index 1c72d81..0000000
--- a/test/contracts/code_errors/last_declaration_must_be_contract.aes
+++ /dev/null
@@ -1,2 +0,0 @@
-namespace LastDeclarationIsNotAContract =
-  function add(x, y) = x + y
diff --git a/test/contracts/code_errors/missing_definition.aes b/test/contracts/code_errors/missing_definition.aes
index 6f7b919..5e354ec 100644
--- a/test/contracts/code_errors/missing_definition.aes
+++ b/test/contracts/code_errors/missing_definition.aes
@@ -1,3 +1,3 @@
 contract MissingDefinition =
   entrypoint foo : int => int
-  entrypoint main() = foo(0)
+  entrypoint main_fun() = foo(0)
diff --git a/test/contracts/code_errors/polymorphic_aens_resolve.aes b/test/contracts/code_errors/polymorphic_aens_resolve.aes
index 6301743..0bd9cc8 100644
--- a/test/contracts/code_errors/polymorphic_aens_resolve.aes
+++ b/test/contracts/code_errors/polymorphic_aens_resolve.aes
@@ -3,5 +3,5 @@ contract PolymorphicAENSresolve =
   function fail() : option('a) =
     AENS.resolve("foo.aet", "whatever")
 
-  entrypoint main() = ()
+  entrypoint main_fun() = ()
 
diff --git a/test/contracts/code_errors/polymorphic_map_keys.aes b/test/contracts/code_errors/polymorphic_map_keys.aes
index eb64237..9821780 100644
--- a/test/contracts/code_errors/polymorphic_map_keys.aes
+++ b/test/contracts/code_errors/polymorphic_map_keys.aes
@@ -3,4 +3,4 @@ contract MapAsMapKey =
 
   function foo(m) : t('a) = {[m] = 0}
 
-  entrypoint main() = ()
+  entrypoint main_fun() = ()
diff --git a/test/contracts/code_errors/polymorphic_query_type.aes b/test/contracts/code_errors/polymorphic_query_type.aes
index 4fba99b..0f5d6ab 100644
--- a/test/contracts/code_errors/polymorphic_query_type.aes
+++ b/test/contracts/code_errors/polymorphic_query_type.aes
@@ -2,4 +2,4 @@ contract PolymorphicQueryType =
   stateful function is_oracle(o) =
     Oracle.check(o)
 
-  entrypoint main() = ()
+  entrypoint main_fun() = ()
diff --git a/test/contracts/code_errors/polymorphic_response_type.aes b/test/contracts/code_errors/polymorphic_response_type.aes
index 9b33971..3c26af5 100644
--- a/test/contracts/code_errors/polymorphic_response_type.aes
+++ b/test/contracts/code_errors/polymorphic_response_type.aes
@@ -2,4 +2,4 @@ contract PolymorphicResponseType =
   function is_oracle(o : oracle(string, 'r)) =
     Oracle.check(o)
 
-  entrypoint main(o : oracle(string, int)) = is_oracle(o)
+  entrypoint main_fun(o : oracle(string, int)) = is_oracle(o)
diff --git a/test/contracts/code_errors/unapplied_contract_call.aes b/test/contracts/code_errors/unapplied_contract_call.aes
index 0ef0248..78f5a12 100644
--- a/test/contracts/code_errors/unapplied_contract_call.aes
+++ b/test/contracts/code_errors/unapplied_contract_call.aes
@@ -1,4 +1,4 @@
-contract Remote =
+contract interface Remote =
   entrypoint foo : int => int
 
 contract UnappliedContractCall =
diff --git a/test/contracts/code_errors/unapplied_named_arg_builtin.aes b/test/contracts/code_errors/unapplied_named_arg_builtin.aes
index 9b0a5ce..ebd2d1a 100644
--- a/test/contracts/code_errors/unapplied_named_arg_builtin.aes
+++ b/test/contracts/code_errors/unapplied_named_arg_builtin.aes
@@ -1,5 +1,5 @@
 contract UnappliedNamedArgBuiltin =
   // Allowed in FATE, but not AEVM
-  stateful entrypoint main(s) =
+  stateful entrypoint main_fun(s) =
     let reg = Oracle.register
     reg(signature = s, Contract.address, 100, RelativeTTL(100)) : oracle(int, int)
diff --git a/test/contracts/complex_types.aes b/test/contracts/complex_types.aes
index 57e19d7..83b9b69 100644
--- a/test/contracts/complex_types.aes
+++ b/test/contracts/complex_types.aes
@@ -1,5 +1,5 @@
 
-contract Remote =
+contract interface Remote =
   entrypoint up_to       : (int)               => list(int)
   entrypoint sum         : (list(int))         => int
   entrypoint some_string : ()                  => string
diff --git a/test/contracts/contract_as_namespace.aes b/test/contracts/contract_as_namespace.aes
index 489dfda..ac4de29 100644
--- a/test/contracts/contract_as_namespace.aes
+++ b/test/contracts/contract_as_namespace.aes
@@ -1,4 +1,4 @@
-contract Foo =
+contract interface Foo =
   entrypoint foo : () => int
 
 contract Fail =
diff --git a/test/contracts/environment.aes b/test/contracts/environment.aes
index d02eec5..a05f5bf 100644
--- a/test/contracts/environment.aes
+++ b/test/contracts/environment.aes
@@ -1,6 +1,6 @@
 
 // Testing primitives for accessing the block chain environment
-contract Interface =
+contract interface Interface =
   entrypoint contract_address : () => address
   entrypoint call_origin      : () => address
   entrypoint call_caller      : () => address
diff --git a/test/contracts/events.aes b/test/contracts/events.aes
index 74a3393..b63397c 100644
--- a/test/contracts/events.aes
+++ b/test/contracts/events.aes
@@ -1,4 +1,4 @@
-contract Remote =
+contract interface Remote =
   entrypoint dummy : () => unit
 
 contract Events =
diff --git a/test/contracts/factorial.aes b/test/contracts/factorial.aes
index 88a8869..800ef07 100644
--- a/test/contracts/factorial.aes
+++ b/test/contracts/factorial.aes
@@ -1,6 +1,6 @@
 // An implementation of the factorial function where each recursive
 // call is to another contract. Not the cheapest way to compute factorial.
-contract FactorialServer =
+contract interface FactorialServer =
   entrypoint fac : (int) => int
 
 contract Factorial =
diff --git a/test/contracts/identity.aes b/test/contracts/identity.aes
index cc5eeaf..2a639f6 100644
--- a/test/contracts/identity.aes
+++ b/test/contracts/identity.aes
@@ -1,3 +1,2 @@
-
-contract Identity =
-  entrypoint main (x:int) = x
+main contract Identity =
+  entrypoint main_fun (x:int) = x
diff --git a/test/contracts/lhs_matching.aes b/test/contracts/lhs_matching.aes
index 2cafa9d..98dddbb 100644
--- a/test/contracts/lhs_matching.aes
+++ b/test/contracts/lhs_matching.aes
@@ -16,7 +16,7 @@ contract LHSMatching =
     let null(_ :: _) = false
     !null(xs)
 
-  entrypoint main() =
+  entrypoint main_fun() =
     from_some(Some([0]))
       ++ append([length([true]), 2, 3], [4, 5, 6])
       ++ [7 | if (local_match([false]))]
diff --git a/test/contracts/missing_event_type.aes b/test/contracts/missing_event_type.aes
index 8931c5e..745fcf4 100644
--- a/test/contracts/missing_event_type.aes
+++ b/test/contracts/missing_event_type.aes
@@ -1,3 +1,3 @@
 contract MissingEventType =
-  entrypoint main() =
+  entrypoint main_fun() =
     Chain.event("MAIN")
diff --git a/test/contracts/multiple_contracts.aes b/test/contracts/multiple_contracts.aes
index 41df9b4..5d71b36 100644
--- a/test/contracts/multiple_contracts.aes
+++ b/test/contracts/multiple_contracts.aes
@@ -1,5 +1,7 @@
-contract ContractOne =
-  entrypoint foo() = "foo"
+contract Child =
+  entrypoint
+        add2 : int => int
+        add2(x) = x + 2
 
-contract ContractTwo =
-  entrypoint bar() = "bar"
+main contract Main =
+  entrypoint add4(x, c : Child) = c.add2(x) + 2
\ No newline at end of file
diff --git a/test/contracts/non_functional_entrypoint.aes b/test/contracts/non_functional_entrypoint.aes
index 4162e38..0b23b5a 100644
--- a/test/contracts/non_functional_entrypoint.aes
+++ b/test/contracts/non_functional_entrypoint.aes
@@ -1,4 +1,4 @@
-contract C1 =
+contract interface C1 =
   entrypoint f : int
 
 contract C =
diff --git a/test/contracts/protected_call.aes b/test/contracts/protected_call.aes
index d377399..6bf09b2 100644
--- a/test/contracts/protected_call.aes
+++ b/test/contracts/protected_call.aes
@@ -1,4 +1,4 @@
-contract Remote =
+contract interface Remote =
   entrypoint id : int => int
 
 contract ProtectedCall =
diff --git a/test/contracts/remote_call.aes b/test/contracts/remote_call.aes
index e644a0f..c5b0547 100644
--- a/test/contracts/remote_call.aes
+++ b/test/contracts/remote_call.aes
@@ -1,18 +1,18 @@
 
-contract Remote1 =
-  entrypoint main : (int) => int
+contract interface Remote1 =
+  entrypoint main_fun : (int) => int
 
-contract Remote2 =
+contract interface Remote2 =
   entrypoint call : (Remote1, int) => int
 
-contract Remote3 =
+contract interface Remote3 =
   entrypoint get : () => int
   entrypoint tick : () => unit
 
 contract RemoteCall =
 
     stateful entrypoint call(r : Remote1, x : int) : int =
-        r.main(gas = 10000, value = 10, x)
+        r.main_fun(gas = 10000, value = 10, x)
 
     entrypoint staged_call(r1 : Remote1, r2 : Remote2, x : int) =
         r2.call(r1, x)
diff --git a/test/contracts/spend_test.aes b/test/contracts/spend_test.aes
index 7213959..0eb1666 100644
--- a/test/contracts/spend_test.aes
+++ b/test/contracts/spend_test.aes
@@ -1,5 +1,5 @@
 
-contract SpendContract =
+contract interface SpendContract =
   entrypoint withdraw : (int) => int
 
 contract SpendTest =
diff --git a/test/contracts/state_handling.aes b/test/contracts/state_handling.aes
index 00c2fcb..67722ba 100644
--- a/test/contracts/state_handling.aes
+++ b/test/contracts/state_handling.aes
@@ -1,5 +1,5 @@
 include "String.aes"
-contract Remote =
+contract interface Remote =
   record rstate = { i : int, s : string, m : map(int, int) }
 
   entrypoint look_at : (rstate) => unit
diff --git a/test/contracts/stateful.aes b/test/contracts/stateful.aes
index e6ea8be..7237b6e 100644
--- a/test/contracts/stateful.aes
+++ b/test/contracts/stateful.aes
@@ -1,5 +1,5 @@
 
-contract Remote =
+contract interface Remote =
   stateful entrypoint remote_spend : (address, int) => unit
   entrypoint remote_pure : int => int
 
diff --git a/test/contracts/test.aes b/test/contracts/test.aes
index bd1a130..c20002f 100644
--- a/test/contracts/test.aes
+++ b/test/contracts/test.aes
@@ -95,7 +95,7 @@ contract Identity =
   function s(n) = (f,x)=>f(n(f,x))
   function add(m,n) = (f,x)=>m(f,n(f,x))
 
-  entrypoint main() =
+  entrypoint main_fun() =
     let three=s(s(s(z)))
     add(three,three)
        (((i)=>i+1),0)
diff --git a/test/contracts/type_clash.aes b/test/contracts/type_clash.aes
index dd20607..fb95e4c 100644
--- a/test/contracts/type_clash.aes
+++ b/test/contracts/type_clash.aes
@@ -1,5 +1,5 @@
 
-contract Remote =
+contract interface Remote =
 
   type themap = map(int, string)
   entrypoint foo : () => themap
diff --git a/test/contracts/unapplied_builtins.aes b/test/contracts/unapplied_builtins.aes
index 678b085..1f2e9ae 100644
--- a/test/contracts/unapplied_builtins.aes
+++ b/test/contracts/unapplied_builtins.aes
@@ -9,7 +9,7 @@
 //    Oracle.extend
 include "String.aes"
 contract UnappliedBuiltins =
-  entrypoint main() = ()
+  entrypoint main_fun() = ()
   type o = oracle(int, int)
   type t = list(int * string)
   type m = map(int, int)