To expand a little, yeah I second this - it's basically never a bluff.
Given that only 10% of your stack is in the pot already, and that he raises big enough to put you in a shove or fold situation, you want to be no worse than flipping to get the money in right?
Here's a range you're flipping with:
99+,AQs+,KQs,AQo+,KQo
If a passive 15/12 is doing this with KQo or 99, I'll eat my hat.