Duplicate tag created when tag slug is changed

On my site, I had posts tagged as ‘photos’ so I could link to /tag/photos and display all posts with photos. For SEO purposes, I now want the slug for that tag to be ‘something-else’ (not really that, but I want the site updater to be able to just type the word ‘photos’ and have it show up with the URL of /tag/something-else). This worked fine for the posts that existed with the tag photos.

However, whenever a new post is created, and the tag ‘photos’ is added, it adds a duplicate ‘photos’ tag with the slug ‘photos’. Obviously, this means all new posts tagged ‘photos’ won’t show up under the URL /tag/something-else which isn’t good.

Does anyone know of a workaround? Any help would be greatly appreciated!

-Michael Nelson