diff --git a/python/ray/worker.py b/python/ray/worker.py
index 8b1d7e1c4..fe65e290a 100644
--- a/python/ray/worker.py
+++ b/python/ray/worker.py
@@ -314,7 +314,7 @@ class Worker(object):
                                        "of their fields. This behavior may "
                                        "be incorrect in some cases.".format(
                                            type(e.example_object)))
-                    logger.warning(warning_message)
+                    logger.debug(warning_message)
                 except (serialization.RayNotDictionarySerializable,
                         serialization.CloudPickleError,
                         pickle.pickle.PicklingError, Exception):