COM ISR not being linked

Good afternoon,

I'm trying to register a serial (com-0) interrupt using uVision 3 on the Cypress FX2LP. The code compiles fine, but the linker warns:

WARNING L16: UNCALLED SEGMENT, IGNORED OVERLAY PROCESS
SEGMENT: ?PR?COM_ISR?MAIN

My ISR looks like this:

static void com_isr (void) interrupt 4 {
        char c;

        if (RI) {
                c = SBUF0;    // read character
                RI = 0;       // clear interrupt request flag
                if (istart + ILEN != iend) {
                inbuf[iend++ & (ILEN-1)] = c;
                }
        }

        if (TI != 0) {
        TI = 0;                  // clear interrupt request flag
        if (ostart != oend) {    // if characters in buffer and
                SBUF0 = outbuf[ostart++ & (OLEN-1)];        // transmit character
                sendfull = 0;
        }
                else {  // if all characters transmitted
                        sendactive = 0;                 // clear 'sendactive'
                }
        }
}

This code is pretty much copy and pasted from the Keil Help section on Serial Transmission.

This ISR is not being called, even with IE=0x80 (to enable global interrupts) and ES0 = 1 (to enable serial 0 interrupts). Does anyone have any suggestions?

Thanks,

Montana