I made the same change to the schema almost a year ago.
The schema change is not in a released version of GW 2012.
It will be available for GW 2012 SP3.
I can give you a copy of the schema, if you would like.
(It would be pretty much the same as what you have.
It might have a few other changes that you probably
wouldn't care about.)
The same change is in GW 2014 that will be released
in the near future.