diff --git a/xen/include/xen/compiler.h b/xen/include/xen/compiler.h
index 6e07990f23..4b3472daee 100644
--- a/xen/include/xen/compiler.h
+++ b/xen/include/xen/compiler.h
@@ -7,8 +7,8 @@
 
 #define barrier()     __asm__ __volatile__("": : :"memory")
 
-#define likely(x)     __builtin_expect((x),1)
-#define unlikely(x)   __builtin_expect((x),0)
+#define likely(x)     __builtin_expect(!!(x),1)
+#define unlikely(x)   __builtin_expect(!!(x),0)
 
 #define inline        __inline__
 #define always_inline __inline__ __attribute__ ((always_inline))