diff --git a/common/macros.h b/common/macros.h
index 84067c5..5dad70a 100644
--- a/common/macros.h
+++ b/common/macros.h
@@ -42,7 +42,7 @@
 ; shorthand
 #define	_OFF_M(o)	((o) - * - 3)
 #define	_BRX_M(o)	<_OFF_M(o), >_OFF_M(o)
-#define	_MRG_M(p, q)	(p) * 16 + (q)
+#define	_MRG_M(p, q)	((p) * 16 + (q))
 
 ; macros
 #define ESC		.BYTE _ESC_C