--- a/hgext/evolve.py	Wed Aug 06 17:39:32 2014 -0700
+++ b/hgext/evolve.py	Wed Aug 06 17:40:55 2014 -0700
@@ -1754,9 +1754,9 @@
         raise util.Abort(_('nothing to prune'))
 
     wlock = lock = None
-    wlock = repo.wlock()
-    sortedrevs = lambda specs: sorted(set(scmutil.revrange(repo, specs)))
     try:
+        wlock = repo.wlock()
+        sortedrevs = lambda specs: sorted(set(scmutil.revrange(repo, specs)))
         lock = repo.lock()
         # defines pruned changesets
         precs = []