--- a/hgext/mq.py	Tue Jan 31 23:13:04 2012 -0600
+++ b/hgext/mq.py	Wed Feb 01 12:20:10 2012 +0100
@@ -1313,6 +1313,10 @@
             if heads != [self.applied[-1].node]:
                 raise util.Abort(_("popping would remove a revision not "
                                    "managed by this patch queue"))
+            if not repo[self.applied[-1].node].mutable():
+                raise util.Abort(
+                    _("popping would remove an immutable revision"),
+                    hint=_('see "hg help phases" for details'))
 
             # we know there are no local changes, so we can make a simplified
             # form of hg.update.
@@ -1374,6 +1378,9 @@
             (top, patchfn) = (self.applied[-1].node, self.applied[-1].name)
             if repo.changelog.heads(top) != [top]:
                 raise util.Abort(_("cannot refresh a revision with children"))
+            if not repo[top].mutable():
+                raise util.Abort(_("cannot refresh immutable revision"),
+                                 hint=_('see "hg help phases" for details'))
 
             inclsubs = self.checksubstate(repo)
 

--- a/tests/test-mq-safety.t	Tue Jan 31 23:13:04 2012 -0600
+++ b/tests/test-mq-safety.t	Wed Feb 01 12:20:10 2012 +0100
@@ -1,5 +1,6 @@
   $ echo '[extensions]' >> $HGRCPATH
-  $ echo 'mq =' >> $HGRCPATH
+  $ echo 'hgext.mq =' >> $HGRCPATH
+  $ echo 'hgext.graphlog =' >> $HGRCPATH
 
   $ hg init repo
   $ cd repo
@@ -17,6 +18,35 @@
   $ echo bar >> foo
   $ hg qrefresh -m 'append bar'
 
+Try to operate on public mq changeset
+
+  $ hg qpop
+  popping bar
+  now at: foo
+  $ hg phase --public qbase
+  $ echo babar >> foo
+  $ hg qref
+  abort: cannot refresh immutable revision
+  (see "hg help phases" for details)
+  [255]
+  $ hg revert -a
+  reverting foo
+  $ hg qpop
+  abort: popping would remove an immutable revision
+  (see "hg help phases" for details)
+  [255]
+  $ hg qfold bar
+  abort: cannot refresh immutable revision
+  (see "hg help phases" for details)
+  [255]
+  $ hg revert -a
+  reverting foo
+
+restore state for remaining test
+
+  $ hg qpush
+  applying bar
+  now at: bar
 
 try to commit on top of a patch