You can try importing can-stache-bindings directly, but I think your issue might be elsewhere, like if you're creating a context around the place where you're doing this binding (like, if you made a stache section)
I had a similar problem recently that made a property undefined all the time, and it was due to a separate definition setter happening that blanked out the value. I don't know if that's your issue, but maybe try commenting out your other defined values