diff --git a/include/asm-powerpc/pmc.h b/include/asm-powerpc/pmc.h
index 2f3c3fc..5f41f3a 100644
--- a/include/asm-powerpc/pmc.h
+++ b/include/asm-powerpc/pmc.h
@@ -22,6 +22,7 @@
 #include <asm/ptrace.h>
 
 typedef void (*perf_irq_t)(struct pt_regs *);
+extern perf_irq_t perf_irq;
 
 int reserve_pmc_hardware(perf_irq_t new_perf_irq);
 void release_pmc_hardware(void);