diff -r ef4538ba67ef -r 00d905a12bb6 mercurial/localrepo.py
--- a/mercurial/localrepo.py	Sun May 17 22:09:37 2015 -0400
+++ b/mercurial/localrepo.py	Wed May 20 04:34:27 2015 +0900
@@ -985,7 +985,7 @@
                                      validator=validate)
 
         trid = 'TXN:' + util.sha1("%s#%f" % (id(tr), time.time())).hexdigest()
-        tr.hookargs['TXNID'] = trid
+        tr.hookargs['txnid'] = trid
         # note: writing the fncache only during finalize mean that the file is
         # outdated when running hooks. As fncache is used for streaming clone,
         # this is not expected to break anything that happen during the hooks.