C++ overloaded virtual function

[Joe Nosay]

/usr/home/raspycat/traverso/work/traverso-0.49.2/src/engine/Driver.h:49:14:
note: hidden overloaded virtual function 'Driver::setup' declared
here: different number of parameters (3 vs 4)
        virtual int setup(bool capture=true, bool playback=true, const
QString& cardDevice="none"

Three = and one &, the last being the odd man out. Both spacing and
removing the & still results in an error.

Clang++ is expecting an absolute value such as the other three.

How do I compensate for the & to have the same value type as =?