diff --git a/vcsserver/lib/rc_cache/backends.py b/vcsserver/lib/rc_cache/backends.py
--- a/vcsserver/lib/rc_cache/backends.py
+++ b/vcsserver/lib/rc_cache/backends.py
@@ -265,7 +265,7 @@ class BaseRedisBackend(redis_backend.Red
 
     def get_mutex(self, key):
         if self.distributed_lock:
-            lock_key = redis_backend.u(u'_lock_{0}'.format(safe_unicode(key)))
+            lock_key = u'_lock_{0}'.format(safe_unicode(key))
             return get_mutex_lock(self.client, lock_key, self._lock_timeout,
                                   auto_renewal=self._lock_auto_renewal)
         else: