diff --git a/src/testdir/test_assert.vim b/src/testdir/test_assert.vim
index 986f0d9..0edcf58 100644
--- a/src/testdir/test_assert.vim
+++ b/src/testdir/test_assert.vim
@@ -127,6 +127,14 @@
   call remove(v:errors, 0)
 endfunc
 
+func Test_override()
+  call test_override('char_avail', 1)
+  call test_override('redraw', 1)
+  call test_override('ALL', 0)
+  call assert_fails("call test_override('xxx', 1)", 'E475')
+  call assert_fails("call test_override('redraw', 'yes')", 'E474')
+endfunc
+
 func Test_user_is_happy()
   smile
   sleep 300m