diff --git a/src/testdir/test_channel.vim b/src/testdir/test_channel.vim
index 431e407..2ed3abf 100644
--- a/src/testdir/test_channel.vim
+++ b/src/testdir/test_channel.vim
@@ -149,6 +149,7 @@
   call ch_setoptions(handle, {'timeout': 1111})
   call assert_fails("call ch_setoptions(handle, {'waittime': 111})", "E475")
   call assert_fails("call ch_setoptions(handle, {'mode': 'json'})", "E475")
+  call ch_setoptions(handle, {'callback': ''})
 
   " Send an eval request that works.
   call assert_equal('ok', ch_sendexpr(handle, 'eval-works'))