diff --git a/base/include/android-base/macros.h b/base/include/android-base/macros.h
index 913a9a0..299ec35 100644
--- a/base/include/android-base/macros.h
+++ b/base/include/android-base/macros.h
@@ -123,8 +123,11 @@
   ((sizeof(a) / sizeof(*(a))) / \
     static_cast<size_t>(!(sizeof(a) % sizeof(*(a)))))
 
-#define LIKELY(x) __builtin_expect((x), true)
-#define UNLIKELY(x) __builtin_expect((x), false)
+// Changing this definition will cause you a lot of pain.  A majority of
+// vendor code defines LIKELY and UNLIKELY this way, and includes
+// this header through an indirect path.
+#define LIKELY( exp )       (__builtin_expect( (exp) != 0, true  ))
+#define UNLIKELY( exp )     (__builtin_expect( (exp) != 0, false ))
 
 #define WARN_UNUSED __attribute__((warn_unused_result))