Index: src/Parser/lex.ll
===================================================================
--- src/Parser/lex.ll	(revision 6253fc3f2d5482a6de2467374f8270a03a4b97e9)
+++ src/Parser/lex.ll	(revision 242f7053d2148bb454ba918531bf1f5e23a8ffc8)
@@ -464,5 +464,5 @@
 void yyerror( const char * errmsg ) {
 	SemanticErrorThrow = true;
-	cout << (yyfilename ? yyfilename : "*unknown file*") << ':' << yylineno << ':' << column - yyleng + 1
+	cerr << (yyfilename ? yyfilename : "*unknown file*") << ':' << yylineno << ':' << column - yyleng + 1
 		 << ": " << ErrorHelpers::error_str() << errmsg << " at token \"" << (yytext[0] == '\0' ? "EOF" : yytext) << '"' << endl;
 }