diff -r 431068d7e9db -r 7eadc9407867 mercurial/ancestor.py
--- a/mercurial/ancestor.py	Sat Sep 08 10:48:42 2018 +0900
+++ b/mercurial/ancestor.py	Sat Sep 08 10:59:24 2018 +0900
@@ -273,7 +273,7 @@
 
         Result does not include the null revision."""
         self._parentrevs = pfunc
-        self._initrevs = revs
+        self._initrevs = revs = [r for r in revs if r >= stoprev]
         self._stoprev = stoprev
         self._inclusive = inclusive