--- a/contrib/perf.py	Sun Nov 11 17:59:23 2018 +0900
+++ b/contrib/perf.py	Mon Nov 19 23:02:29 2018 +0000
@@ -1404,7 +1404,7 @@
             ui.popbuffer()
         diffopt = diffopt.encode('ascii')
         title = b'diffopts: %s' % (diffopt and (b'-' + diffopt) or b'none')
-        timer(d, title)
+        timer(d, title=title)
     fm.end()
 
 @command(b'perfrevlogindex', revlogopts + formatteropts,