MSP-EXP430F5529LP: Setting up interrupt vector for the UART on USCI_A1

Hi, on an MSP-EXP430F5529LP board, compiling using gcc, I'm setting up interrupt routines for both TIMER B and USCI A. I'm using code like:

// USCI A1
__attribute__ ((interrupt(USCI_A1_VECTOR)))
void USCI_A1_ISR (void)
{
code
}

// TIMER B CC
__attribute__ ((interrupt(TIMER0_B0_VECTOR)))
void TIMER0_B0_ISR (void)
{
code
}

Now when compiled, the code has:

Disassembly of section __interrupt_vector_60:

0000fff6 <__interrupt_vector_60>:
    fff6:       08 47           interrupt service routine at 0x4708

So its got an interrupt for Timer B, but it doesn't create one for USCI A. I can see both are defined in msp430f5529.h

#define USCI_A1_VECTOR          (47)                     /* 0xFFDC USCI A1 Receive/Transmit */
#define TIMER0_B0_VECTOR        (60)                     /* 0xFFF6 Timer0_B7 CC0 */

So what am I doing wrong, its as though the USCI interrupt code is just left out - e.g. it hasn't picked up that its and interrupt routine.