diff --git a/sgsn/SGSN_Tests.ttcn b/sgsn/SGSN_Tests.ttcn
index c47403e..cf354a7 100644
--- a/sgsn/SGSN_Tests.ttcn
+++ b/sgsn/SGSN_Tests.ttcn
@@ -149,7 +149,7 @@
 		imsi := f_gen_imsi(imsi_suffix),
 		msisdn := f_gen_msisdn(imsi_suffix),
 		p_tmsi := omit,
-		tlli := 'FFFFFFFF'O,
+		tlli := f_gprs_tlli_random(),
 		ra := omit,
 		bssgp_cell_id := gb.cfg.cell_id,
 		vec := omit,