diff --git a/library/RLCMAC_Templates.ttcn b/library/RLCMAC_Templates.ttcn
index a4cd993..5e27341 100644
--- a/library/RLCMAC_Templates.ttcn
+++ b/library/RLCMAC_Templates.ttcn
@@ -705,7 +705,7 @@
 		}
 	};
 
-	template RlcmacDlBlock tr_RLCMAC_UL_ACK_NACK_GPRS(template uint5_t ul_tfi, template UlAckNackGprs gprs := tr_UlAckNackGprs(*))
+	template RlcmacDlBlock tr_RLCMAC_UL_ACK_NACK_GPRS(template uint5_t ul_tfi := ?, template UlAckNackGprs gprs := tr_UlAckNackGprs(*))
 	modifies tr_RLCMAC_UL_ACK_NACK := {
 		ctrl := {
 			payload := {
@@ -720,7 +720,7 @@
 		}
 	};
 
-	template RlcmacDlBlock tr_RLCMAC_UL_ACK_NACK_EGPRS(template uint5_t ul_tfi, template UlAckNackEgprs egprs := tr_UlAckNackEgprs(*))
+	template RlcmacDlBlock tr_RLCMAC_UL_ACK_NACK_EGPRS(template uint5_t ul_tfi := ?, template UlAckNackEgprs egprs := tr_UlAckNackEgprs(*))
 	modifies tr_RLCMAC_UL_ACK_NACK := {
 		ctrl := {
 			payload := {