Is the vanity access code case sensitive?

Subject says it all. Sorry if this has been asked before, but I couldn't find anything in a search.

All of the codes I have seen are in uppercase. I entered mine in as lower case, but when I try to change it to upper case it says that code is in use. I was wondering if there is another channel with the same code in uppercase or if the code validation in the web app is not working correctly.