--- a/hgext3rd/evolve/obsdiscovery.py	Sun Mar 12 08:38:39 2017 -0700
+++ b/hgext3rd/evolve/obsdiscovery.py	Sat Mar 11 14:46:27 2017 -0800
@@ -557,15 +557,28 @@
 
         cl = self._repo.changelog
 
+        result = []
         bottom = self._revs[:localindex]
-        top = self._revs[localindex:]
-        bheads = self._repo.revs('heads(%ld)', bottom)
-        result = []
+        top = _range(self._repo, self.head, globalindex, self._revs[localindex:])
+        #
+        toprootdepth = utility.depth(self._repo, top._revs[0])
+        if toprootdepth + len(top) == self.depth + 1:
+            bheads = [bottom[-1]]
+        else:
+            bheads = set(bottom)
+            parentrevs = cl.parentrevs
+            du = bheads.difference_update
+            for r in bottom:
+                du(parentrevs(r))
+            # if len(bheads) == 1:
+            #     assert 1 == len(self._repo.revs('roots(%ld)', top._revs))
         if len(bheads) == 1:
             newhead = bottom[-1]
-            newstart = utility.depth(self._repo, newhead) - len(bottom)
+            bottomdepth = utility.depth(self._repo, newhead)
+            newstart = bottomdepth - len(bottom)
             result.append(_range(self._repo, newhead, newstart, bottom))
         else:
+            # assert 1 < len(bheads), (toprootdepth, len(top), len(self))
             cl = self._repo.changelog
             for h in bheads:
                 subset = cl.ancestors([h], inclusive=True)
@@ -573,7 +586,7 @@
                 start = utility.depth(self._repo, h) - len(hrevs)
                 entry = _range(self._repo, h, start, [r for r in bottom if r in subset])
                 result.append(entry)
-        result.append(_range(self._repo, self.head, globalindex, top))
+        result.append(top)
         return result
 
     def subranges(self):