Editing a question title does not change SEO URL if I only append text to the title

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I posted a question on my hosted site a couple of weeks ago, initially entitled New Requirements for Panama Permanent Residency.

To improve SEO a bit, I added some keywords to the title and renamed it to "New Requirements for Panama Permanent Residency under Executive Decree 343".

However, I notice that the SEO URL did not get updated:

http://expats.askbot.com/question/69/new-requirements-for-panama-permanent-residency/

The updated title should be:

http://expats.askbot.com/question/69/new-requirements-for-panama-permanent-residency-under-executive-decree-343/

EDIT: I did some test edits on this question to try to nail down the behavior. It looks like if I edit the text in the title, the SEO URL is updated, but if I only append text to the title, the SEO URL is unaffected.