diff --git a/pcu/GPRS_TBF.ttcn b/pcu/GPRS_TBF.ttcn
index fb42097..f946f29 100644
--- a/pcu/GPRS_TBF.ttcn
+++ b/pcu/GPRS_TBF.ttcn
@@ -326,10 +326,10 @@
 
 	/* include TLLI when needed */
 	if (tlli_needed) {
-		blk := valueof(t_RLCMAC_UL_DATA_TLLI(us.tfi, cv, us.et.v_s,
+		blk := valueof(t_RLCMAC_UL_DATA_TLLI(CS_1, us.tfi, cv, us.et.v_s,
 						llc_blocks, false, mmctx.tlli));
 	} else {
-		blk := valueof(t_RLCMAC_UL_DATA(us.tfi, cv, us.et.v_s, llc_blocks, false));
+		blk := valueof(t_RLCMAC_UL_DATA(CS_1, us.tfi, cv, us.et.v_s, llc_blocks, false));
 	}
 
 	/* Increment Block Sequence Number */