imagefield_image_field_settings_form not getting called

When the field form is being generated, the function imagefield_image_field_settings_form is not getting called. This is because when the filefield module is looking for candidate callbacks, it searches for .inc files of the format field-type_field.inc. However, for imagefields the type is 'image', not 'imagefield' so imagefield_field.inc does not get loaded.

Is this a bug in the field type, or is the filename itself incorrect?