CC2530: Macro concatenation with "=" does not create a valid token

Part Number:CC2530

Hello,

I'm using the IAR Workbench and I just wanna know how to avoid the below warning: 

Warning[Pe1665]: concatenation with "=" in macro "MCU_IO_OUTPUT_PREP" does not create a valid token 

In the follow code:

#define MCU_IO_OUTPUT_PREP(port, pin, val) st( P##port##SEL &= ~BM(pin); \
P##port##_##pin## = val; \
P##port##DIR |= BM(pin); )

the definition of "st()" is:

#define st(x)      do { x } while (__LINE__ == -1)

Please any help, 

Best regards and thanks a lot for your help