diff --git a/toltec/bash.py b/toltec/bash.py
index 52c66c1..1f6f094 100644
--- a/toltec/bash.py
+++ b/toltec/bash.py
@@ -144,8 +144,17 @@ def get_declarations(src: str) -> Tuple[Variables, Functions]:
             if name not in default_variables:
                 variables[name] = value
         else:
-            assert next_token == "("
-            assert lexer.get_token() == ")"
+            if next_token != "(":
+                raise ScriptError(
+                    f"Unexpected token '{next_token}' on line {lexer.lineno}. Expecting '('."
+                )
+
+            _token = lexer.get_token()
+            if _token != ")":
+                raise ScriptError(
+                    f"Unexpected token '{_token}' on line {lexer.lineno}. Expecting ')'."
+                )
+
             start, end = _parse_func(lexer)
             functions[token] = declarations[start:end].strip(" ")