diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index c20f69a4c5e9..0a367fa23c27 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2082,8 +2082,12 @@ static void gsm0_receive(struct gsm_mux *gsm, unsigned char c)
 		break;
 	case GSM_DATA:		/* Data */
 		gsm->buf[gsm->count++] = c;
-		if (gsm->count == gsm->len)
+		if (gsm->count >= MAX_MRU) {
+			gsm->bad_size++;
+			gsm->state = GSM_SEARCH;
+		} else if (gsm->count >= gsm->len) {
 			gsm->state = GSM_FCS;
+		}
 		break;
 	case GSM_FCS:		/* FCS follows the packet */
 		gsm->received_fcs = c;
@@ -2176,7 +2180,7 @@ static void gsm1_receive(struct gsm_mux *gsm, unsigned char c)
 		gsm->state = GSM_DATA;
 		break;
 	case GSM_DATA:		/* Data */
-		if (gsm->count > gsm->mru) {	/* Allow one for the FCS */
+		if (gsm->count > gsm->mru || gsm->count > MAX_MRU) {	/* Allow one for the FCS */
 			gsm->state = GSM_OVERRUN;
 			gsm->bad_size++;
 		} else