diff --git a/core/parser.py b/core/parser.py
index 4582d8f..3d6be35 100755
--- a/core/parser.py
+++ b/core/parser.py
@@ -51,7 +51,7 @@ def try_register(self, res: ParseResult[U]) -> Optional[U]:
             return None
         return self.register(res)
 
-    def success(self, node: T) -> ParseResult[T]:
+    def success(self, node: T) -> Optional[ParseResult[T]]:
         self.node = node
         return self