--- a/hgext/evolve.py	Mon Apr 25 16:24:42 2016 -0700
+++ b/hgext/evolve.py	Mon Apr 25 16:24:42 2016 -0700
@@ -2509,9 +2509,8 @@
         if not precs:
             raise error.Abort('nothing to prune')
 
-        if not obsolete.isenabled(repo, obsolete.allowunstableopt):
-            if repo.revs("(%ld::) - %ld", revs, revs):
-                raise error.Abort(_("cannot prune in the middle of a stack"))
+        if _disallowednewunstable(repo, revs):
+            raise error.Abort(_("cannot prune in the middle of a stack"))
 
         # defines successors changesets
         sucs = scmutil.revrange(repo, succs)
@@ -3172,13 +3171,17 @@
         raise error.Abort(_("cannot fold non-linear revisions "
                            "(multiple heads given)"))
     head = repo[heads.first()]
-    disallowunstable = not obsolete.isenabled(repo, obsolete.allowunstableopt)
-    if disallowunstable:
-        if repo.revs("(%ld::) - %ld", revs, revs):
-            raise error.Abort(_("cannot fold chain not ending with a head "\
-                               "or with branching"))
+    if _disallowednewunstable(repo, revs):
+        raise error.Abort(_("cannot fold chain not ending with a head "\
+                            "or with branching"))
     return root, head
 
+def _disallowednewunstable(repo, revs):
+    allowunstable = obsolete.isenabled(repo, obsolete.allowunstableopt)
+    if allowunstable:
+        return revset.baseset()
+    return repo.revs("(%ld::) - %ld", revs, revs)
+
 @eh.wrapcommand('graft')
 def graftwrapper(orig, ui, repo, *revs, **kwargs):
     kwargs = dict(kwargs)