diff --git a/bts/BTS_Tests.ttcn b/bts/BTS_Tests.ttcn
index 4f0f0ef..941be28 100644
--- a/bts/BTS_Tests.ttcn
+++ b/bts/BTS_Tests.ttcn
@@ -3658,7 +3658,7 @@
 	/* now we actually need to transmit some data both ways to check if the encryption works */
 	var L1ctlDlMessage dl;
 
-	var octetstring l3 := f_rnd_octstring(16);
+	var octetstring l3 := f_rnd_octstring(20);
 	var RslLinkId link_id := valueof(ts_RslLinkID_DCCH(0));
 
 	/* send UNITDATA_REQ from BTS to MS and expect it to arrive */