--- a/hgext/obsolete.py	Tue Aug 21 02:25:19 2012 +0200
+++ b/hgext/obsolete.py	Tue Aug 21 02:50:11 2012 +0200
@@ -955,10 +955,15 @@
 
 def buildstate(orig, repo, dest, rebaseset, *ags, **kws):
     """wrapper for rebase 's buildstate that exclude obsolete changeset"""
+
     rebaseset = repo.revs('%ld - extinct()', rebaseset)
     if not rebaseset:
         repo.ui.warn(_('whole rebase set is extinct and ignored.\n'))
         return {}
+    root = min(rebaseset)
+    if not repo._rebasekeep and not repo[root].mutable():
+        raise util.Abort(_("can't rebase immutable changeset %s") % repo[root],
+                         hint=_('see hg help phases for details'))
     return orig(repo, dest, rebaseset, *ags, **kws)
 
 def defineparents(orig, repo, rev, target, state, *args, **kwargs):
@@ -985,6 +990,7 @@
     reallykeep = kwargs.get('keep', False)
     kwargs = dict(kwargs)
     kwargs['keep'] = True
+    repo._rebasekeep = reallykeep
 
     # We want to mark rebased revision as obsolete and set their
     # replacements if any. Doing it in concludenode() prevents