diff --git a/openbsc/src/gprs/gprs_gmm.c b/openbsc/src/gprs/gprs_gmm.c
index 72239e0..3977c66 100644
--- a/openbsc/src/gprs/gprs_gmm.c
+++ b/openbsc/src/gprs/gprs_gmm.c
@@ -57,6 +57,9 @@
 
 #define PTMSI_ALLOC
 
+/* Section 11.2.2 / Table 11.3a GPRS Mobility management timers – MS side */
+#define GSM0408_T3312_SECS	(10*60)	/* periodic RAU interval, default 54min */
+
 /* Section 11.2.2 / Table 11.4 MM timers netwokr side */
 #define GSM0408_T3322_SECS	6	/* DETACH_REQ -> DETACH_ACC */
 #define GSM0408_T3350_SECS	6	/* waiting for ATT/RAU/TMSI COMPL */
@@ -327,7 +330,7 @@
 	aa = (struct gsm48_attach_ack *) msgb_put(msg, sizeof(*aa));
 	aa->force_stby = 0;	/* not indicated */
 	aa->att_result = 1;	/* GPRS only */
-	aa->ra_upd_timer = GPRS_TMR_MINUTE | 10;
+	aa->ra_upd_timer = gprs_secs_to_tmr_floor(GSM0408_T3312_SECS);
 	aa->radio_prio = 4;	/* lowest */
 	gsm48_construct_ra(aa->ra_id.digits, &mm->ra);
 
@@ -978,7 +981,7 @@
 	rua = (struct gsm48_ra_upd_ack *) msgb_put(msg, sizeof(*rua));
 	rua->force_stby = 0;	/* not indicated */
 	rua->upd_result = 0;	/* RA updated */
-	rua->ra_upd_timer = GPRS_TMR_MINUTE | 10;
+	rua->ra_upd_timer = gprs_secs_to_tmr_floor(GSM0408_T3312_SECS);
 
 	gsm48_construct_ra(rua->ra_id.digits, &mm->ra);