--- a/mercurial/hg.py	Sat Mar 12 04:35:42 2016 +0900
+++ b/mercurial/hg.py	Sat Mar 12 04:35:42 2016 +0900
@@ -714,7 +714,7 @@
 
     This returns whether conflict is detected at updating or not.
     """
-    if True:
+    with repo.wlock():
         movemarkfrom = None
         warndest = False
         if checkout is None: