Building Firmware V18 for KBPM

I am trying to build firmware v18. I have installed the Arduino fork and downloaded the v18 release zip. When I make I get an error while building PCInterrupt.o

PCInterrupt.cpp:42:4: error: ‘PCMSK1’ was not declared in this scope
   &PCMSK1,
    ^
PCInterrupt.cpp:43:4: error: ‘PCMSK2’ was not declared in this scope
   &PCMSK2
    ^
Makefile:408: recipe for target 'PCInterrupt.o' failed
make: *** [PCInterrupt.o] Error 1

Any ideas?