--- a/mercurial/store.py	Thu Oct 15 20:36:12 2015 -0400
+++ b/mercurial/store.py	Wed Oct 14 22:29:03 2015 -0400
@@ -404,7 +404,7 @@
             fp.seek(0)
             for n, line in enumerate(fp):
                 if not line.rstrip('\n'):
-                    t = _('invalid entry in fncache, line %s') % (n + 1)
+                    t = _('invalid entry in fncache, line %d') % (n + 1)
                     raise error.Abort(t)
         fp.close()