diff --git a/lotus/cache.py b/lotus/cache.py
index b5b85c7e..609c6f0f 100644
--- a/lotus/cache.py
+++ b/lotus/cache.py
@@ -59,7 +59,7 @@ def serialize(value: Any) -> Any:
                     lotus.logger.warning(f"Unsupported type {type(value)} for serialization. Converting to string.")
                     return str(value)
 
-            serialize_self = serialize(self)
+            serialize_self = serialize(self._obj)
             serialized_kwargs = {key: serialize(value) for key, value in kwargs.items()}
             serialized_args = [serialize(arg) for arg in args]
             cache_key = hashlib.sha256(