Do wwatch and rwatch accept only absolute addresses?

I tried using the symbol name in a wwatch expression and the signal function would not execute past that line

unsigned char xdata SMBflag=0;
( locates to X:0x0000)

signal void Int1(void){
while(1){
wwatch(SMBflag);
SI = 1;
swatch(5);
SI = 0;
swatch(5);
}
}

void main (void);
{
while(1){
SMBflag++;
while(SI){
;
}
wait_for_10sec();
}
}

The signal function never executed with the symbol SMBflag but when X:0x0000 was used as an argument it ran fine. I've seen an example on the Keil website for an I2C memory which uses symbols as arguments but I couldn't get it to work either. Am I missing simething obvious here?