--- a/tests/test-topic.t	Mon Mar 21 21:39:14 2016 -0700
+++ b/tests/test-topic.t	Wed Mar 30 03:56:14 2016 -0700
@@ -6,6 +6,11 @@
   > [phases]
   > publish=false
   > EOF
+  $ cat <<EOF >> $HGRCPATH
+  > [experimental]
+  > # disable the new graph style until we drop 3.7 support
+  > graphstyle.missing = |
+  > EOF
 
   $ hg help topics
   hg topics [TOPIC]