diff --git a/src/protocol/parser/pass_symbols.rs b/src/protocol/parser/pass_symbols.rs
index 94ee54a7c0c228d208db3434750b56b7351c7f4b..3210f1b578465bbc046d758b649bae82aa6c3cb5 100644
--- a/src/protocol/parser/pass_symbols.rs
+++ b/src/protocol/parser/pass_symbols.rs
@@ -185,7 +185,7 @@ impl PassSymbols {
         maybe_consume_comma_separated(
             TokenKind::OpenAngle, TokenKind::CloseAngle, &module.source, &mut iter,
             |source, iter| consume_ident_interned(source, iter, ctx),
-            &mut poly_vars, "a polymorphic variable"
+            &mut poly_vars, "a polymorphic variable", None
         )?;
         let ident_text = identifier.value.clone(); // because we need it later