1 files changed, 2 insertions, 0 deletions
diff --git a/calc.erl b/calc.erl
index 04ac38f..4869104 100644
--- a/calc.erl
+++ b/calc.erl
@@ -17,6 +17,8 @@ num(Input, Num) ->
 %% bracket := [-] ( '(' sum '}' | num )
 bracket([$-|Input]) ->
     case bracket(Input) of
+	{ok, {Tail, []}} ->
+	    {error, {expected_number, {before, Tail}}};
 	{ok, {Tail, Result}} ->
 	    {ok, {Tail, -1 * Result}};
 	{error, Why} ->