diff --git a/openbsc/src/gprs/gprs_gmm.c b/openbsc/src/gprs/gprs_gmm.c
index d93ba3f..9d94c24 100644
--- a/openbsc/src/gprs/gprs_gmm.c
+++ b/openbsc/src/gprs/gprs_gmm.c
@@ -2089,7 +2089,7 @@
 int gsm0408_gprs_rcvmsg(struct msgb *msg, struct gprs_llc_llme *llme)
 {
 	struct gsm48_hdr *gh = (struct gsm48_hdr *) msgb_gmmh(msg);
-	uint8_t pdisc = gh->proto_discr & 0x0f;
+	uint8_t pdisc = gsm48_hdr_pdisc(gh);
 	struct sgsn_mm_ctx *mmctx;
 	struct gprs_ra_id ra_id;
 	int rc = -EINVAL;