diff --git a/ChangeLog b/ChangeLog
index f0fd418d30..acdf0b0474 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Thu Jul  4 00:13:01 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* ruby_atomic.h (rb_w32_atomic_cas): call InterlockedCompareExchange
+	  directly.
+
+	* ruby_atomic.h (ATOMIC_CAS): fix missing function call.
+
 Wed Jul  3 23:47:35 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* ruby_atomic.h (ATOMIC_CAS): suppress C4022 and C4047 warnings in
diff --git a/ruby_atomic.h b/ruby_atomic.h
index 53273a4026..9bf5e035bb 100644
--- a/ruby_atomic.h
+++ b/ruby_atomic.h
@@ -54,10 +54,10 @@ rb_w32_atomic_or(volatile rb_atomic_t *var, rb_atomic_t val)
 static inline rb_atomic_t
 rb_w32_atomic_cas(volatile rb_atomic_t *var, rb_atomic_t oldval, rb_atomic_t newval)
 {
-    return (rb_atomic_t)ATOMIC_CAS(*(PVOID *)var, (PVOID)oldval, (PVOID)(newval));
+    return (rb_atomic_t)InterlockedCompareExchange((PVOID *)var, (PVOID)newval, (PVOID)oldval);
 }
 #   undef ATOMIC_CAS
-#   define ATOMIC_CAS(var, oldval, newval) (&(var), (newval), (oldval))
+#   define ATOMIC_CAS(var, oldval, newval) rb_w32_atomic_cas(&(var), (oldval), (newval))
 # endif
 # ifdef _M_AMD64
 #  define ATOMIC_SIZE_ADD(var, val) InterlockedExchangeAdd64(&(var), (val))