--- a/tests/test-uncommit.t	Tue Jul 11 11:59:18 2017 +0200
+++ b/tests/test-uncommit.t	Tue Jul 11 12:00:45 2017 +0200
@@ -384,3 +384,16 @@
   date:        Thu Jan 01 00:22:17 1970 +0000
   summary:     to-uncommit
   
+
+test -U option
+
+  $ hg uncommit -U b
+  $ hg log -r .
+  changeset:   14:288da4a95941
+  branch:      bar
+  tag:         tip
+  parent:      7:4f1c269eab68
+  user:        test
+  date:        Thu Jan 01 00:22:17 1970 +0000
+  summary:     to-uncommit
+