diff --git a/openbsc/src/gprs/gprs_gmm.c b/openbsc/src/gprs/gprs_gmm.c
index 036164f..efa25c6 100644
--- a/openbsc/src/gprs/gprs_gmm.c
+++ b/openbsc/src/gprs/gprs_gmm.c
@@ -874,8 +874,10 @@
 		goto err_inval;
 	cur += msnc_len;
 
+	/* TODO: In iu mode - handle follow-on request */
+
 	/* aTTACH Type 10.5.5.2 */
-	att_type = *cur++ & 0x0f;
+	att_type = *cur++ & 0x07;
 
 	/* DRX parameter 10.5.5.6 */
 	drx_par = *cur++ << 8;
@@ -1171,8 +1173,10 @@
 	enum gsm48_gmm_cause reject_cause;
 	int rc;
 
+	/* TODO: In iu mode - handle follow-on request */
+
 	/* Update Type 10.5.5.18 */
-	upd_type = *cur++ & 0x0f;
+	upd_type = *cur++ & 0x07;
 
 	rate_ctr_inc(&sgsn->rate_ctrs->ctr[CTR_GPRS_ROUTING_AREA_REQUEST]);
 	LOGP(DMM, LOGL_INFO, "-> GMM RA UPDATE REQUEST type=\"%s\"\n",