--- a/tests/test-grab.t	Sat Mar 03 23:31:46 2018 +0530
+++ b/tests/test-grab.t	Tue Mar 13 20:44:51 2018 +0530
@@ -47,6 +47,12 @@
   abort: cannot grab an ancestor revision
   [255]
 
+Grabbing the working directory parent
+
+  $ hg grab -r .
+  abort: cannot grab an ancestor revision
+  [255]
+
 Specifying multiple revisions to grab
 
   $ hg grab 1f0dee641bb7 -r 7c3bad9141dc