diff --git a/nilmdb/utils/serializer.py b/nilmdb/utils/serializer.py
index 0e04e14..3f74180 100644
--- a/nilmdb/utils/serializer.py
+++ b/nilmdb/utils/serializer.py
@@ -118,8 +118,8 @@ def serializer_proxy(obj_or_type):
 
         def __del__(self):
             try:
+                # Signal thread to exit, but don't wait for it.
                 self.__call_queue.put((None, None, None, None))
-                self.__thread.join()
             except: # pragma: no cover
                 pass