diff --git a/include/asm-x86/hw_irq.h b/include/asm-x86/hw_irq.h
index a8c5e8b..cdb09d7 100644
--- a/include/asm-x86/hw_irq.h
+++ b/include/asm-x86/hw_irq.h
@@ -67,6 +67,10 @@
 extern int IO_APIC_get_PCI_irq_vector(int bus, int slot, int fn);
 extern void setup_ioapic_dest(void);
 
+#ifdef CONFIG_X86_64
+extern void enable_IO_APIC(void);
+#endif
+
 /* IPI functions */
 extern void send_IPI_self(int vector);
 extern void send_IPI(int dest, int vector);