diff --git a/src/gsm/gsm0808.c b/src/gsm/gsm0808.c
index 9cd70a0..eae1598 100644
--- a/src/gsm/gsm0808.c
+++ b/src/gsm/gsm0808.c
@@ -159,7 +159,7 @@
 	if (!msg)
 		return NULL;
 
-	msg->l3h = msgb_put(msg, 3);
+	msg->l3h = msgb_put(msg, 4);
 	msg->l3h[0] = BSSAP_MSG_BSS_MANAGEMENT;
 	msg->l3h[1] = 2;
 	msg->l3h[2] = BSS_MAP_MSG_CIPHER_MODE_REJECT;