diff --git a/pcap-client/OPCAP_CLIENT_Tests.ttcn b/pcap-client/OPCAP_CLIENT_Tests.ttcn
index e9fe406..1efc343 100644
--- a/pcap-client/OPCAP_CLIENT_Tests.ttcn
+++ b/pcap-client/OPCAP_CLIENT_Tests.ttcn
@@ -144,7 +144,7 @@
 		var octetstring udp_payload;
 
 		/* we assume 1400 is low enough to avoid IP fragmentation */
-		udp_payload := f_rnd_octstring(f_rnd_int(1400));
+		udp_payload := f_rnd_octstring_rnd_len(1400);
 		f_trafic_pkt_ab(udp_payload);
 
 		f_opcap_exp_udp(udp_payload, 0);
@@ -173,7 +173,7 @@
 		var octetstring udp_payload;
 
 		/* we assume 1400 is low enough to avoid IP fragmentation */
-		udp_payload := f_rnd_octstring(f_rnd_int(1400));
+		udp_payload := f_rnd_octstring_rnd_len(1400);
 		f_trafic_pkt_ab(udp_payload);
 
 		/* expect packet to arrive on both simulated servers */