diff --git a/lib/locking.py b/lib/locking.py
index df6219aca3b5e24eee30e816d4324296ed7ef61b..647e14f4c030b393dc3addfe144bfa645c5e8627 100644
--- a/lib/locking.py
+++ b/lib/locking.py
@@ -451,7 +451,7 @@ class LockSet:
       if isinstance(names, basestring):
         names = [names]
       else:
-        names.sort()
+        names = sorted(names)
 
       acquire_list = []
       # First we look the locks up on __lockdict. We have no way of being sure