diff --git a/src/aeso_ast_to_fcode.erl b/src/aeso_ast_to_fcode.erl
index b478822..218fc7d 100644
--- a/src/aeso_ast_to_fcode.erl
+++ b/src/aeso_ast_to_fcode.erl
@@ -25,6 +25,7 @@
 -type sophia_name() :: [string()].
 
 -type binop() :: '+' | '-' | '==' | '::'.
+-type unop() :: '!'.
 
 -type fexpr() :: {int, integer()}
                | {string, binary()}
@@ -39,7 +40,8 @@
                | {tuple, [fexpr()]}
                | {proj, fexpr(), integer()}
                | {set_proj, fexpr(), integer(), fexpr()}    %% tuple, field, new_value
-               | {binop, binop(), fexpr(), fexpr()}
+               | {op, binop(), fexpr(), fexpr()}
+               | {op, unop(), fexpr()}
                | {'let', var_name(), fexpr(), fexpr()}
                | {switch, fsplit()}.
 
@@ -360,7 +362,12 @@ expr_to_fcode(Env, _Type, {block, _, Stmts}) ->
 %% Binary operator
 expr_to_fcode(Env, _Type, {app, _Ann, {Op, _}, [A, B]}) when is_atom(Op) ->
     FOp = binop_to_fcode(Op),
-    {binop, FOp, expr_to_fcode(Env, A), expr_to_fcode(Env, B)};
+    {op, FOp, expr_to_fcode(Env, A), expr_to_fcode(Env, B)};
+expr_to_fcode(Env, _Type, {app, _Ann, {Op, _}, [A]}) when is_atom(Op) ->
+    case Op of
+        '-' -> {op, '-', {int, 0}, expr_to_fcode(Env, A)};
+        '!' -> {op, '!', expr_to_fcode(Env, A)}
+    end;
 
 expr_to_fcode(_Env, Type, Expr) ->
     error({todo, {Expr, ':', Type}}).
diff --git a/src/aeso_fcode_to_fate.erl b/src/aeso_fcode_to_fate.erl
index e134e5d..58cf387 100644
--- a/src/aeso_fcode_to_fate.erl
+++ b/src/aeso_fcode_to_fate.erl
@@ -217,10 +217,13 @@ to_scode(Env, {set_proj, R, I, E}) ->
      to_scode(Env, R),
      aeb_fate_code:setelement(?a, ?i(I), ?a, ?a)];
 
-to_scode(Env, {binop, Op, A, B}) ->
+to_scode(Env, {op, Op, A, B}) ->
     [ to_scode(notail(Env), B),
-      to_scode(Env, A),
+      to_scode(notail(Env), A),
       binop_to_scode(Op) ];
+to_scode(Env, {op, Op, A}) ->
+    [ to_scode(notail(Env), A),
+      unop_to_scode(Op) ];
 
 to_scode(Env, {'let', X, {var, Y}, Body}) ->
     Env1 = bind_var(X, lookup_var(Env, Y), Env),
@@ -351,7 +354,8 @@ binop_to_scode('+') -> aeb_fate_code:add(?a, ?a, ?a);
 binop_to_scode('-') -> aeb_fate_code:sub(?a, ?a, ?a);
 binop_to_scode('==') -> aeb_fate_code:eq(?a, ?a, ?a);
 binop_to_scode('::') -> aeb_fate_code:cons(?a, ?a, ?a).
-% binop_to_scode(Op) -> ?TODO(Op).
+
+unop_to_scode('!') -> aeb_fate_code:not_op(?a, ?a).
 
 %% -- Phase II ---------------------------------------------------------------
 %%  Optimize