My fault, I'm trying to restart the build from a different environment to usual and I messed up the change. It should be there now (and build restarted).
No worries - I see, in this case the append was the right thing. One day I'll get these right on the first try. One day! Thanks for the fix.
Yeah... += with an over-ride is intuitive but 99.9% of the time is completely wrong.
There was a discussion some time ago about having the parser reject it with an error because it repeatedly trips up new (and some not so new...) developers, but it never came to anything.