diff --git a/openbsc/src/gprs/gprs_gsup_messages.c b/openbsc/src/gprs/gprs_gsup_messages.c
index f47ad55..1dad74f 100644
--- a/openbsc/src/gprs/gprs_gsup_messages.c
+++ b/openbsc/src/gprs/gprs_gsup_messages.c
@@ -74,7 +74,7 @@
 
 		rc = gprs_shift_tlv(&data, &data_len, &tag, &value, &value_len);
 		if (rc < 0)
-			return rc;
+			return -GMM_CAUSE_PROTO_ERR_UNSPEC;
 
 		iei = tag;
 
@@ -116,7 +116,7 @@
 	while (data_len > 0) {
 		rc = gprs_shift_tlv(&data, &data_len, &tag, &value, &value_len);
 		if (rc < 0)
-			return rc;
+			return -GMM_CAUSE_PROTO_ERR_UNSPEC;
 
 		iei = tag;