Simple boolean expression parser in Spirit

Question

I've come up with following boolean expression parser after reading the Spirit tutorials:

expression =
          bool_                           [_val =  _1]
            >> *(  ("&&" >> expression    [_val && _1])
                |  ("||" >> expression    [_val || _1])
                )
            ;

For constants I get the correct results from the parser:

true -> 1

false -> 0

But for slightly more complex expressions things go horribly wrong:

true && false -> 1 (incorrect!)

false && true -> 0 (correct)

false || true -> 0 (incorrect!)

true || false -> 1 (correct)