--- a/mercurial/commands.py	Sat Sep 30 15:46:36 2017 +0530
+++ b/mercurial/commands.py	Sat Sep 30 18:02:53 2017 +0530
@@ -2150,7 +2150,7 @@
     skipped = set()
     # check for merges
     for rev in repo.revs('%ld and merge()', revs):
-        ui.warn(_('skipping ungraftable merge revision %s\n') % rev)
+        ui.warn(_('skipping ungraftable merge revision %d\n') % rev)
         skipped.add(rev)
     revs = [r for r in revs if r not in skipped]
     if not revs: