diff --git a/src/testdir/test_channel.vim b/src/testdir/test_channel.vim
index 065e8b4..6fa7e3b 100644
--- a/src/testdir/test_channel.vim
+++ b/src/testdir/test_channel.vim
@@ -163,11 +163,11 @@
   eval handle->ch_setoptions({'callback': 's:NotUsed'})
   call ch_setoptions(handle, {'timeout': 1111})
   call ch_setoptions(handle, {'mode': 'json'})
-  call assert_fails("call ch_setoptions(handle, {'waittime': 111})", "E475")
+  call assert_fails("call ch_setoptions(handle, {'waittime': 111})", 'E475:')
   call ch_setoptions(handle, {'callback': ''})
   call ch_setoptions(handle, {'drop': 'never'})
   call ch_setoptions(handle, {'drop': 'auto'})
-  call assert_fails("call ch_setoptions(handle, {'drop': 'bad'})", "E475")
+  call assert_fails("call ch_setoptions(handle, {'drop': 'bad'})", 'E475:')
   call assert_equal(0, ch_setoptions(handle, test_null_dict()))
   call assert_equal(0, ch_setoptions(test_null_channel(), {'drop' : 'never'}))