diff --git a/include/osmocore/protocol/gsm_03_41.h b/include/osmocore/protocol/gsm_03_41.h
index 3b1b7c9..54365cb 100644
--- a/include/osmocore/protocol/gsm_03_41.h
+++ b/include/osmocore/protocol/gsm_03_41.h
@@ -40,7 +40,7 @@
 	uint8_t data[0];
 } __attribute__((packed));
 
-#define GSM341_MSG_CODE(ms) (ms->serial.code_lo | (msg->serial.code_hi << 4))
+#define GSM341_MSG_CODE(ms) ((ms)->serial.code_lo | ((ms)->serial.code_hi << 4))
 
 /* Section 9.3.2.1 - Geographical Scope */
 #define GSM341_GS_CELL_WIDE_IMMED	0