jLightbox does not appear in selectlist

I added jLightbox to an existing and working site with cck, imagefield and imagecache. On the admin/content/types//display page the jLightbox options did not appear in the image display select list. From looking at the code it appeared that the options in the select list are cached and the cache is not flushed (function content_clear_type_cache). As a workaround I went to the imagecache administration page and updated one of the presets. Now the imagefield display select list showed the jLightbox options.
I see other modules clear the cache in the .install file (number, text, userreference). Perhaps this is an option for jLightbox.