diff -r cc81c512a531 -r 89075f106414 mercurial/commands.py
--- a/mercurial/commands.py	Mon Mar 19 19:07:39 2007 -0300
+++ b/mercurial/commands.py	Mon Mar 19 19:07:40 2007 -0300
@@ -764,7 +764,11 @@
     if not rev2:
         rev2 = hex(nullid)
 
-    repo.dirstate.setparents(repo.lookup(rev1), repo.lookup(rev2))
+    wlock = repo.wlock()
+    try:
+        repo.dirstate.setparents(repo.lookup(rev1), repo.lookup(rev2))
+    finally:
+        wlock.release()
 
 def debugstate(ui, repo):
     """show the contents of the current dirstate"""