diff --git a/src/testdir/test_functions.vim b/src/testdir/test_functions.vim
index 14181fb..41996bd 100644
--- a/src/testdir/test_functions.vim
+++ b/src/testdir/test_functions.vim
@@ -464,6 +464,18 @@
   call assert_equal('n', mode(0))
   call assert_equal('n', mode(1))
 
+  " i_CTRL-O
+  exe "normal i\<C-O>:call Save_mode()\<Cr>\<Esc>"
+  call assert_equal("n-niI", g:current_modes)
+
+  " R_CTRL-O
+  exe "normal R\<C-O>:call Save_mode()\<Cr>\<Esc>"
+  call assert_equal("n-niR", g:current_modes)
+
+  " gR_CTRL-O
+  exe "normal gR\<C-O>:call Save_mode()\<Cr>\<Esc>"
+  call assert_equal("n-niV", g:current_modes)
+
   " How to test operator-pending mode?
 
   call feedkeys("v", 'xt')