--- a/contrib/perf.py	Thu Feb 22 01:00:57 2018 -0500
+++ b/contrib/perf.py	Wed Feb 21 12:13:16 2018 +0100
@@ -1616,7 +1616,10 @@
     branchcachewrite.set(lambda bc, repo: None)
     try:
         for name in allfilters:
-            timer(getbranchmap(name), title=str(name))
+            printname = name
+            if name is None:
+                printname = 'unfiltered'
+            timer(getbranchmap(name), title=str(printname))
     finally:
         branchcacheread.restore()
         branchcachewrite.restore()