diff --git a/src/aeso_compiler.erl b/src/aeso_compiler.erl
index 0280edd..1703d40 100644
--- a/src/aeso_compiler.erl
+++ b/src/aeso_compiler.erl
@@ -36,6 +36,7 @@
                 | pp_assembler
                 | pp_bytecode
                 | no_code
+                | no_implicit_stdlib
                 | {backend, aevm | fate}
                 | {include, {file_system, [string()]} |
                             {explicit_files, #{string() => binary()}}}
diff --git a/src/aeso_parser.erl b/src/aeso_parser.erl
index de71794..4cce718 100644
--- a/src/aeso_parser.erl
+++ b/src/aeso_parser.erl
@@ -6,6 +6,7 @@
 
 -export([string/1,
          string/2,
+         string/3,
          type/1]).
 
 -include("aeso_parse_lib.hrl").
@@ -16,13 +17,25 @@
 
 -spec string(string()) -> parse_result().
 string(String) ->
-    string(String, []).
+    string(String, sets:new(), []).
 
--spec string(string(), aeso_compiler:options()) -> parse_result().
+
+-spec string(string(), compiler:options()) -> parse_result().
 string(String, Opts) ->
+    string(String, sets:new(), Opts).
+
+-spec string(string(), sets:set(string()), aeso_compiler:options()) -> parse_result().
+string(String, Included, Opts) ->
     case parse_and_scan(file(), String, Opts) of
         {ok, AST} ->
-            expand_includes(AST, Opts);
+            STD = case lists:member(no_implicit_stdlib, Opts) of
+                      false -> [{ include, [{src_file, File}, {origin, system}]
+                                , {string, [{src_file, File}, {origin, system}], File}}
+                                || {File, _} <- aeso_stdlib:stdlib_list()
+                               ];
+                      true -> []
+                  end,
+            expand_includes(STD ++ AST, Included, Opts);
         Err = {error, _} ->
             Err
     end.
@@ -230,7 +243,7 @@ exprAtom() ->
         , {bool, keyword(false), false}
         , ?LET_P(Fs, brace_list(?LAZY_P(field_assignment())), record(Fs))
         , {list, [], bracket_list(Expr)}
-        , ?RULE(keyword('['), Expr, tok('|'), comma_sep(?LAZY_P(comprehension_bind())), tok(']'), list_comp_e(_1, _2, _4))
+        , ?RULE(keyword('['), Expr, token('|'), comma_sep(?LAZY_P(comprehension_bind())), tok(']'), list_comp_e(_1, _2, _4))
         , ?RULE(tok('['), Expr, binop('..'), Expr, tok(']'), _3(_2, _4))
         , ?RULE(keyword('('), comma_sep(Expr), tok(')'), tuple_e(_1, _2))
         ])
@@ -527,35 +540,40 @@ bad_expr_err(Reason, E) ->
                             prettypr:nest(2, aeso_pretty:expr(E))])).
 
 %% -- Helper functions -------------------------------------------------------
-expand_includes(AST, Opts) ->
-    expand_includes(AST, [], Opts).
+expand_includes(AST, Included, Opts) ->
+    expand_includes(AST, Included, [], Opts).
 
-expand_includes([], Acc, _Opts) ->
+expand_includes([], _Included, Acc, _Opts) ->
     {ok, lists:reverse(Acc)};
-expand_includes([{include, Ann, S = {string, _, File}} | AST], Acc, Opts) ->
-    case {read_file(File, Opts), maps:find(File, aeso_stdlib:stdlib())} of
-        {{ok, _}, {ok,_ }} ->
-            return_error(ann_pos(Ann), "Illegal redefinition of standard library " ++ File);
-        {_, {ok, Lib}} ->
-            case string(Lib) of
-                {ok, AST1} ->
-                    expand_includes(AST1 ++ AST, Acc, Opts);
-                Err = {error, _} ->
-                    Err
-            end;
-        {{ok, Bin}, _} ->
+expand_includes([{include, Ann, S = {string, _, File}} | AST], Included, Acc, Opts) ->
+    case sets:is_element(File, Included) of
+        false ->
             Opts1 = lists:keystore(src_file, 1, Opts, {src_file, File}),
-            case string(binary_to_list(Bin), Opts1) of
-                {ok, AST1} ->
-                    expand_includes(AST1 ++ AST, Acc, Opts);
-                Err = {error, _} ->
-                    Err
+            Included1 = sets:add_element(File, Included),
+            case {read_file(File, Opts), maps:find(File, aeso_stdlib:stdlib())} of
+                {{ok, _}, {ok,_ }} ->
+                    return_error(ann_pos(Ann), "Illegal redefinition of standard library " ++ File);
+                     {_, {ok, Lib}} ->
+                    case string(Lib, Included1, Opts1) of
+                        {ok, AST1} ->
+                            expand_includes(AST1 ++ AST, Included1, Acc, Opts);
+                        Err = {error, _} ->
+                            Err
+                    end;
+                {{ok, Bin}, _} ->
+                    case string(binary_to_list(Bin), Included1, Opts1) of
+                        {ok, AST1} ->
+                            expand_includes(AST1 ++ AST, Included1, Acc, Opts);
+                        Err = {error, _} ->
+                            Err
+                    end;
+                {_, _} ->
+                    {error, {get_pos(S), include_error, File}}
             end;
-        {{error, _}, _} ->
-            {error, {get_pos(S), include_error, File}}
+        true -> expand_includes(AST, Included, Acc, Opts)
     end;
-expand_includes([E | AST], Acc, Opts) ->
-    expand_includes(AST, [E | Acc], Opts).
+expand_includes([E | AST], Included, Acc, Opts) ->
+    expand_includes(AST, Included, [E | Acc], Opts).
 
 read_file(File, Opts) ->
     case proplists:get_value(include, Opts, {explicit_files, #{}}) of
diff --git a/src/aeso_stdlib.erl b/src/aeso_stdlib.erl
index e726840..4988b54 100644
--- a/src/aeso_stdlib.erl
+++ b/src/aeso_stdlib.erl
@@ -10,14 +10,15 @@
 
 -module(aeso_stdlib).
 
--export([stdlib/0]).
+-export([stdlib/0, stdlib_list/0]).
 
 stdlib() ->
-    maps:from_list(
-      [ {<<"List.aes">>, std_list()}
-     %% , {<<"Func.aes">>, std_function()}
-      ]
-     ).
+    maps:from_list(stdlib_list()).
+
+stdlib_list() ->
+    [ {<<"List.aes">>, std_list()}
+      %% , {<<"Func.aes">>, std_function()}
+    ].
 
 std_function() ->
 "
@@ -51,7 +52,8 @@ namespace Func =
 ".
 
 std_list() ->
-"
+"namespace List =\n  function flat_map() = 3\n".
+x() ->"
 namespace List =
 
   function empty(l) = switch(l)
diff --git a/test/aeso_aci_tests.erl b/test/aeso_aci_tests.erl
index ee719be..0faef0e 100644
--- a/test/aeso_aci_tests.erl
+++ b/test/aeso_aci_tests.erl
@@ -9,7 +9,7 @@ simple_aci_test_() ->
 
 test_contract(N) ->
     {Contract,MapACI,DecACI} = test_cases(N),
-    {ok,JSON} = aeso_aci:contract_interface(json, Contract),
+    {ok,JSON} = aeso_aci:contract_interface(json, Contract, [no_implicit_stdlib]),
     ?assertEqual([MapACI], JSON),
     ?assertEqual({ok, DecACI}, aeso_aci:render_aci_json(JSON)).
 
@@ -98,7 +98,7 @@ aci_test_contract(Name) ->
     {ok, ContractStub} = aeso_aci:render_aci_json(JSON),
 
     io:format("STUB:\n~s\n", [ContractStub]),
-    check_stub(ContractStub, [{src_file, Name}]),
+    check_stub(ContractStub, [{src_file, Name}, no_implicit_stdlib]),
 
     ok.
 
diff --git a/test/aeso_parser_tests.erl b/test/aeso_parser_tests.erl
index dcbbcd0..9b54d94 100644
--- a/test/aeso_parser_tests.erl
+++ b/test/aeso_parser_tests.erl
@@ -15,7 +15,7 @@ simple_contracts_test_() ->
             ?assertMatch(
                 [{contract, _, {con, _, "Identity"},
                     [{letfun, _, {id, _, "id"}, [{arg, _, {id, _, "x"}, {id, _, "_"}}], {id, _, "_"},
-                        {id, _, "x"}}]}], parse_string(Text)),
+                        {id, _, "x"}}]}], parse_string(Text, [no_implicit_stdlib])),
             ok
        end},
       {"Operator precedence test.",
@@ -71,21 +71,23 @@ parse_contract(Name) ->
 roundtrip_contract(Name) ->
     round_trip(aeso_test_utils:read_contract(Name)).
 
-parse_string(Text) ->
-    case aeso_parser:string(Text) of
+parse_string(Text) -> parse_string(Text, []).
+
+parse_string(Text, Opts) ->
+    case aeso_parser:string(Text, Opts) of
         {ok, Contract} -> Contract;
         Err -> error(Err)
     end.
 
 parse_expr(Text) ->
     [{letval, _, _, _, Expr}] =
-        parse_string("let _ = " ++ Text),
+        parse_string("let _ = " ++ Text, [no_implicit_stdlib]),
     Expr.
 
 round_trip(Text) ->
-    Contract  = parse_string(Text),
+    Contract  = parse_string(Text, [no_implicit_stdlib]),
     Text1     = prettypr:format(aeso_pretty:decls(Contract)),
-    Contract1 = parse_string(Text1),
+    Contract1 = parse_string(Text1, [no_implicit_stdlib]),
     NoSrcLoc  = remove_line_numbers(Contract),
     NoSrcLoc1 = remove_line_numbers(Contract1),
     ?assertMatch(NoSrcLoc, diff(NoSrcLoc, NoSrcLoc1)).