diff --git a/google/auth/_refresh_worker.py b/google/auth/_refresh_worker.py
index 9bb0ccc2c..674032d84 100644
--- a/google/auth/_refresh_worker.py
+++ b/google/auth/_refresh_worker.py
@@ -75,7 +75,7 @@ def __getstate__(self):
 
     def __setstate__(self, state):
         """Pickle helper that deserializes the _lock attribute."""
-        state["_key"] = threading.Lock()
+        state["_lock"] = threading.Lock()
         self.__dict__.update(state)
 
 
diff --git a/system_tests/secrets.tar.enc b/system_tests/secrets.tar.enc
index 506ef1415..79c9bb6b6 100644
Binary files a/system_tests/secrets.tar.enc and b/system_tests/secrets.tar.enc differ
diff --git a/tests/test__refresh_worker.py b/tests/test__refresh_worker.py
index f842b02ca..c25965d10 100644
--- a/tests/test__refresh_worker.py
+++ b/tests/test__refresh_worker.py
@@ -150,7 +150,10 @@ def test_refresh_dead_worker():
 
 def test_pickle():
     w = _refresh_worker.RefreshThreadManager()
+    # For some reason isinstance cannot interpret threading.Lock as a type.
+    assert w._lock is not None
 
     pickled_manager = pickle.dumps(w)
     manager = pickle.loads(pickled_manager)
     assert isinstance(manager, _refresh_worker.RefreshThreadManager)
+    assert manager._lock is not None