diff -r df838803c1d4 -r fe50341de1ff tests/test-rollback.t
--- a/tests/test-rollback.t	Tue May 03 09:49:54 2016 -0700
+++ b/tests/test-rollback.t	Tue May 03 16:33:25 2016 -0400
@@ -196,3 +196,15 @@
   checking files
   1 files, 2 changesets, 2 total revisions
 
+rollback disabled by config
+  $ cat >> $HGRCPATH <<EOF
+  > [ui]
+  > rollback = false
+  > EOF
+  $ echo narf >> pinky-sayings.txt
+  $ hg add pinky-sayings.txt
+  $ hg ci -m 'First one.'
+  $ hg rollback
+  abort: rollback is disabled because it is unsafe
+  (see `hg help -v rollback` for information)
+  [255]