diff --git a/python/pydantic_core/core_schema.py b/python/pydantic_core/core_schema.py
index 298b4f3ec..a04427e0c 100644
--- a/python/pydantic_core/core_schema.py
+++ b/python/pydantic_core/core_schema.py
@@ -145,7 +145,7 @@ def context(self) -> ContextT:
         ...
 
     @property
-    def mode(self) -> Literal['python', 'json'] | str:
+    def mode(self) -> Literal['python', 'json']:
         """The serialization mode set during serialization."""
         ...