I have a subversion externals entry in a library folder which looks like this:

Z https://svn/Z/trunk/library/Z

Fetching external item into '/home/releases/50/library/Z' 
svn: OPTIONS of 'http://svn/repo/trunk/library/Z': could not connect to server (http://svn)

The externals URL was the same, but over the HTTP protocol. Having changed the externals to point to the HTTPS, I can't figure out why subversion is still trying to use the old URL.

Does subversion cache the externals path, and if so how can I clear this? If not, what else could be causing this?

I can check out from the correct (HTTPS) URL fine from the server.

NOTE: svn is an entry in the server's local hosts file, pointing to our subversion server's IP.