No warning displayed if filesize too big. Just 'OK, your image was created' ... NOT!

This may be a duplicate, but I couldn't find it in the queue.
I'm trying out a brand-new D6 install, so I hadn't bumped up my file size limit yet.
I Know that 800+ KB for an image is mad, but my job at the moment is to take raw megapixel input, and shrink them on the server.
So image_import goes great - turns out it ignores the filesize. Which is fine by me.

But I go to replace one image, and I just get "Your image has been created" ... and an empty page.
After a mess around and a head-slap, I track it to the file size. OK, fair enough.

But can we get a warning message? Your file is too big!

... logged in as admin, totally fresh D6 & image DRUPAL-6