--- a/mercurial/revset.py	Sat Jun 23 13:19:03 2018 +0100
+++ b/mercurial/revset.py	Fri Jun 29 23:13:23 2018 +0900
@@ -319,8 +319,9 @@
     for r in reviter:
         anc = anc.ancestor(repo[r])
 
-    if anc.rev() in subset:
-        return baseset([anc.rev()])
+    r = scmutil.intrev(anc)
+    if r in subset:
+        return baseset([r])
     return baseset()
 
 def _ancestors(repo, subset, x, followfirst=False, startdepth=None,