diff --git a/schala-lang/src/parsing/combinator.rs b/schala-lang/src/parsing/combinator.rs
index 1d1643b..f7475b6 100644
--- a/schala-lang/src/parsing/combinator.rs
+++ b/schala-lang/src/parsing/combinator.rs
@@ -503,11 +503,14 @@ fn extended_expr_part(input: Span) -> ParseResult<ExtendedPart> {
     fn call_part(input: Span) -> ParseResult<Vec<InvocationArgument>> {
         context(
             "call-part",
-            //TODO generalize this `not`
-            delimited(
-                tok(char('(')),
-                separated_list0(tok(char(',')), preceded(not(tok(char(')'))), invocation_argument)),
-                tok(char(')')),
+            verify(
+                //TODO generalize this `not`
+                delimited(
+                    tok(char('(')),
+                    separated_list0(tok(char(',')), preceded(not(tok(char(')'))), invocation_argument)),
+                    tok(char(')')),
+                ),
+                |output: &Vec<_>| output.len() <= 255,
             ),
         )(input)
     }
diff --git a/schala-lang/src/parsing/test.rs b/schala-lang/src/parsing/test.rs
index 14d8d88..f7c5b91 100644
--- a/schala-lang/src/parsing/test.rs
+++ b/schala-lang/src/parsing/test.rs
@@ -113,6 +113,7 @@ macro_rules! assert_ast {
     };
 }
 
+/*
 macro_rules! assert_fail {
     ($input:expr, $failure:expr) => {
         let mut parser = Parser::new();
@@ -120,8 +121,13 @@ macro_rules! assert_fail {
         assert_eq!(err.msg, $failure);
     };
 }
+*/
 
-macro_rules! assert_fail_comb {
+macro_rules! assert_fail {
+    ($input:expr) => {
+        let mut parser = Parser::new();
+        let err = parser.parse_comb($input).unwrap_err();
+    };
     ($input:expr, $failure:expr) => {
         let mut parser = Parser::new();
         let err = parser.parse_comb($input).unwrap_err();
@@ -557,7 +563,7 @@ fn complex_lambdas() {
 #[test]
 fn reserved_words() {
     let err = "0: at line 1, in Verify:\nmodule::item::call()\n^\n\n1: at line 1, in tok:\nmodule::item::call()\n^\n\n2: at line 1, in tok:\nmodule::item::call()\n^\n\n3: at line 1, in primary-expr-no-struct:\nmodule::item::call()\n^\n\n4: at line 1, in primary-expr:\nmodule::item::call()\n^\n\n5: at line 1, in extended-expr:\nmodule::item::call()\n^\n\n6: at line 1, in prefix-expr:\nmodule::item::call()\n^\n\n7: at line 1, in expression-kind:\nmodule::item::call()\n^\n\n8: at line 1, in Parsing-statement:\nmodule::item::call()\n^\n\n9: at line 1, in AST:\nmodule::item::call()\n^\n\n";
-    assert_fail_comb!("module::item::call()", err);
+    assert_fail!("module::item::call()", err);
 
     assert_expr!("modulek::item", expr(ExpressionKind::Value(qn!(modulek, item))));
 }
@@ -824,7 +830,7 @@ fn functions() {
         })
     );
     let err_msg = "0: at line 1, in Alpha:\na(b,,c)\n    ^\n\n1: at line 1, in Alt:\na(b,,c)\n    ^\n\n2: at line 1, in tok:\na(b,,c)\n    ^\n\n3: at line 1, in identifier-expr:\na(b,,c)\n    ^\n\n4: at line 1, in Alt:\na(b,,c)\n    ^\n\n5: at line 1, in primary-expr:\na(b,,c)\n    ^\n\n6: at line 1, in extended-expr:\na(b,,c)\n    ^\n\n7: at line 1, in prefix-expr:\na(b,,c)\n    ^\n\n8: at line 1, in expression-kind:\na(b,,c)\n    ^\n\n9: at line 1, in Alt:\na(b,,c)\n    ^\n\n10: at line 1, in invocation-argument:\na(b,,c)\n    ^\n\n11: at line 1, in call-part:\na(b,,c)\n ^\n\n12: at line 1, in extended-expr:\na(b,,c)\n^\n\n13: at line 1, in prefix-expr:\na(b,,c)\n^\n\n14: at line 1, in expression-kind:\na(b,,c)\n^\n\n15: at line 1, in Parsing-statement:\na(b,,c)\n^\n\n16: at line 1, in AST:\na(b,,c)\n^\n\n";
-    assert_fail_comb!("a(b,,c)", err_msg);
+    assert_fail!("a(b,,c)", err_msg);
 
     assert_ast!(
         "fn a(b, c: Int): Int",
@@ -868,8 +874,8 @@ fn max_function_params() {
     }
     write!(buf, ") {{ return 20 }}").unwrap();
     //assert_fail!(&buf, "A function cannot have more than 255 arguments");
-    //TODO better errors again
-    assert_fail!(&buf, "error at 1:1439: expected ['a' ..= 'z' | 'A' ..= 'Z' | '_']");
+    //TODO need to create a good, custom error message for this case
+    assert_fail!(&buf);
 }
 
 #[test]