diff --git a/include/asm-mips/serial.h b/include/asm-mips/serial.h
index 7b23664..0197062 100644
--- a/include/asm-mips/serial.h
+++ b/include/asm-mips/serial.h
@@ -11,6 +11,14 @@
 
 #include <linux/config.h>
 
+#ifdef CONFIG_SOC_AU1X00
+/*
+ * We have to redefine "is_real_interrupt()" for Au1x00 CPUs...
+ */
+#undef is_real_interrupt
+#define is_real_interrupt(irq)	((irq) != ~0)
+#endif
+
 /*
  * This assumes you have a 1.8432 MHz clock for your UART.
  *