diff --git a/src/gboml/parsing.py b/src/gboml/parsing.py
index 1421beeee8cc734890e17e11ad91b759cb6a9c71..9c14e01c0dc9af20ba1ed5ecdc1dfb4a7f30b580 100644
--- a/src/gboml/parsing.py
+++ b/src/gboml/parsing.py
@@ -182,7 +182,7 @@ def _lark_to_gboml(tree: Tree, filename: Optional[str] = None) -> GBOMLGraph:
             for name, import_from in zip(names, imports_from or repeat(None, len(names))):
                 yield VariableDefinition(scope, type or VarType.continuous, name, import_from, tags, meta=meta)
 
-        def variables_block(self, _: Meta, *defs: list[Iterable[VariableDefinition]]):
+        def variables_block(self, _: Meta, *defs: Tuple[Iterable[VariableDefinition]]):
             return [vd for iterable in defs for vd in iterable]
 
         def multi_loop(self, meta: Meta, *loops: Tuple[Loop]):