diff --git a/vsexprtools/variables.py b/vsexprtools/variables.py
index bc3c5af..95c4eba 100644
--- a/vsexprtools/variables.py
+++ b/vsexprtools/variables.py
@@ -30,7 +30,7 @@ class ExprVar(int):
     parent_expr: inline_expr | None
 
     def __new__(
-        cls, x: ByteData, __parent_expr: inline_expr | None, /, *args: Any, **kwargs: Any
+        cls, x: ByteData, __parent_expr: inline_expr | None = None, /, *args: Any, **kwargs: Any
     ) -> ExprVar:
         return super().__new__(cls, 0)