Gick, Barney. I'm glad we're out of that phase...
As for telling Matt? Yes. If you have to ask, you know you need to talk about it (Good lord, do I sound like my mother right there...). If you bring it up now, I hardly think receiving an upset email from Si would be held against you. If you don't? And respond back? Then yeah... that could certainly be construed as being secretive.