diff --git a/ext/v8/rr.h b/ext/v8/rr.h
index a4e8d44..6338729 100644
--- a/ext/v8/rr.h
+++ b/ext/v8/rr.h
@@ -6,7 +6,7 @@
 
 namespace rr {
 
-VALUE Bool(bool);
+VALUE Bool(bool b);
 
 class GC {
 public: