Text in description field is lost during image preview/submit

When attaching a new image initiated from fckeditor, in the popup window the complete node/add/image-page is shown. Along with title and image itself goes the description field, the node's body. I fill a description into it. Proceeding to the next step "preview", the description field is emptied. Same happens, if the preview is skipped. Next page shows another empty field called "description (optional)" which is only used as img_attach-label. The text inserted here persists, but only on the page where the image is inserted. But calling the image node, neither the orginal description nor the img_attach-description is kept, it's just lost.

If this behaviour is "by design", switching off the description-field would be a good idea. Better option would be to keep the description and use it as default for optinal img_attach-description.