diff --git a/include/osmocom/gsm/protocol/gsm_03_41.h b/include/osmocom/gsm/protocol/gsm_03_41.h
index 816017c..3fec997 100644
--- a/include/osmocom/gsm/protocol/gsm_03_41.h
+++ b/include/osmocom/gsm/protocol/gsm_03_41.h
@@ -2,8 +2,13 @@
 
 #include <stdint.h>
 
+#include <osmocom/gsm/protocol/gsm_04_12.h>
+
 /* GSM TS 03.41 definitions also TS 23.041*/
 
+#define GSM341_MAX_PAYLOAD	(GSM412_MSG_LEN-sizeof(struct gsm341_ms_message))
+#define GSM341_MAX_CHARS	(GSM341_MAX_PAYLOAD*8/7)
+
 /* Chapter 9.3.2 */
 struct gsm341_ms_message {
 	struct {
diff --git a/include/osmocom/gsm/protocol/gsm_04_12.h b/include/osmocom/gsm/protocol/gsm_04_12.h
index aa40648..30d6e4f 100644
--- a/include/osmocom/gsm/protocol/gsm_04_12.h
+++ b/include/osmocom/gsm/protocol/gsm_04_12.h
@@ -4,6 +4,9 @@
 
 /* GSM TS 04.12 definitions for Short Message Service Cell Broadcast */
 
+#define GSM412_MSG_LEN		88	/* TS 04.12 Section 3.1 */
+#define GSM412_BLOCK_LEN	22	/* TS 04.12 Section 3.1 */
+
 #define GSM412_SEQ_FST_BLOCK		0x0
 #define GSM412_SEQ_SND_BLOCK		0x1
 #define GSM412_SEQ_TRD_BLOCK		0x2