Brace matching problem

In my Scheme language plugin, I've implemented a PairedBraceMatcher, which works great in normal editors. However it doesn't work in my language console, and I can't figure out why - none of the methods are called. It seems to be related to if the current state of the console is valid or not:

> (

Doesn't add a matching paren here

> (define x (

Or here. But if I close the two parens, making the construct valid, then syntax highlighting kicks in and things start working:

> (define x ())

This is now valid, it gets highlighted correctly, and parens are correctly inserted:

> (define x (()))

I checked that my parser doesn't return an error on empty file, I'm not sure what else to look for.