Quick question about "undefined reference to `alt_ic_isr_register'"

Hi!

I wonder if someone know why i keep getting this error message: "undefined reference to `alt_ic_isr_register'". I have included the library <sys/alt_irq.h>, is there anything else i should do? I am trying to implement an Avalon MM slave with interrupts in Quartus 9.1sp2.

Regards