diff --git a/src/gsm0480.c b/src/gsm0480.c
index 73be8ac..4b1471f 100644
--- a/src/gsm0480.c
+++ b/src/gsm0480.c
@@ -386,6 +386,12 @@
 	int num_chars;
 	uint8_t dcs;
 
+
+	/* we need at least that much */
+	if (length < 8)
+		return 0;
+
+
 	if (uss_req_data[0] == GSM_0480_SEQUENCE_TAG) {
 		if (uss_req_data[2] == ASN1_OCTET_STRING_TAG) {
 			dcs = uss_req_data[4];