--- a/hgext3rd/topic/stack.py	Thu Sep 12 14:42:38 2019 +0700
+++ b/hgext3rd/topic/stack.py	Thu Sep 12 14:44:19 2019 +0700
@@ -200,10 +200,9 @@
 
     @util.propertycache
     def behindcount(self):
-        revs = self.revs[1:]
         deps, rdeps = self._dependencies
-        if revs:
-            minroot = [min(r for r in revs if not deps[r])]
+        if self._revs:
+            minroot = [min(r for r in self._revs if not deps[r])]
             try:
                 dest = destutil.destmerge(self._repo, action=b'rebase',
                                           sourceset=minroot,