--- a/mercurial/cmdutil.py	Sat Mar 14 19:38:59 2015 +0900
+++ b/mercurial/cmdutil.py	Sat Mar 14 17:29:48 2015 +0900
@@ -1237,7 +1237,7 @@
             return parents
         if self.ui.debugflag:
             return [parents[0], self.repo['null']]
-        if parents[0].rev() >= ctx.rev() - 1:
+        if parents[0].rev() >= scmutil.intrev(self.repo, ctx.rev()) - 1:
             return []
         return parents