diff --git a/langgraph/graph/state.py b/langgraph/graph/state.py
index 6c42e139e..cb240b1e2 100644
--- a/langgraph/graph/state.py
+++ b/langgraph/graph/state.py
@@ -180,7 +180,7 @@ class CompiledStateGraph(CompiledGraph):
 
         return super().get_input_schema(config)
 
-    def get_output_schema(self, config: RunnableConfig | None = None) -> BaseModel:
+    def get_output_schema(self, config: Optional[RunnableConfig] = None) -> BaseModel:
         if isinstance(self.builder.schema, BaseModel):
             return self.builder.schema