diff --git a/src/testdir/test_marks.in b/src/testdir/test_marks.in
index 341f3ac..23c2fb6 100644
--- a/src/testdir/test_marks.in
+++ b/src/testdir/test_marks.in
@@ -8,11 +8,27 @@
 madduu
 :let a = string(getpos("'a"))
 :$put ='Mark after delete-undo-redo-undo: '.a
-:/^\t/,$wq! test.out
+:''
 ENDTEST
 
 	textline A
 	textline B
 	textline C
 
+STARTTEST
+:" test that CTRL-A and CTRL-X updates last changed mark '[, '].
+:/^123/
+:execute "normal! \<C-A>`[v`]rAjwvjw\<C-X>`[v`]rX"
+ENDTEST
+
+CTRL-A CTRL-X:
+123 123 123
+123 123 123
+123 123 123
+
+STARTTEST
+:g/^STARTTEST/.,/^ENDTEST/d
+:wq! test.out
+ENDTEST
+
 Results:
diff --git a/src/testdir/test_marks.ok b/src/testdir/test_marks.ok
index dd1a3e4..e6c02ee 100644
--- a/src/testdir/test_marks.ok
+++ b/src/testdir/test_marks.ok
@@ -1,6 +1,16 @@
+Tests for marks.
+
+
 	textline A
 	textline B
 	textline C
 
+
+CTRL-A CTRL-X:
+AAA 123 123
+123 XXXXXXX
+XXX 123 123
+
+
 Results:
 Mark after delete-undo-redo-undo: [0, 15, 2, 0]