diff --git a/ggsn_tests/GGSN_Tests.ttcn b/ggsn_tests/GGSN_Tests.ttcn
index 3b34c7f..ae24eeb 100644
--- a/ggsn_tests/GGSN_Tests.ttcn
+++ b/ggsn_tests/GGSN_Tests.ttcn
@@ -1475,7 +1475,7 @@
 		var PdpContext ctxB := valueof(t_DefinePDP(f_rnd_imsi('26242'H), '1234'O, c_ApnInternet, valueof(t_EuaIPv4Dyn)));
 		f_pdp_ctx_act(ctxA);
 
-		g_restart_ctr := int2oct(oct2int(g_restart_ctr) + 1, 1);
+		g_restart_ctr := int2oct((oct2int(g_restart_ctr) + 1) mod 256, 1);
 
 		log("sending 2nd CreatePDP (recovery increased)");
 		f_send_gtpc(ts_GTPC_CreatePDP(g_peer_c, g_c_seq_nr, ctxB.imsi, g_restart_ctr,
@@ -1564,7 +1564,7 @@
 		/* Wait to receive second echo request and send incremented Restart
 		   counter. This will fake a restarted SGSN, and pdp ctx allocated
 		   should be released by GGSN */
-		g_restart_ctr := int2oct(oct2int(g_restart_ctr) + 1, 1);
+		g_restart_ctr := int2oct((oct2int(g_restart_ctr) + 1) mod 256, 1);
 		GTPC.receive(tr_GTPC_PING(?)) -> value ud {
 			var uint16_t seq := oct2int(ud.gtpc.opt_part.sequenceNumber);
 			GTPC.send(ts_GTPC_PONG(ud.peer, seq, g_restart_ctr));