diff --git a/library/RSL_Types.ttcn b/library/RSL_Types.ttcn
index 5afabe1..cd4ba58 100644
--- a/library/RSL_Types.ttcn
+++ b/library/RSL_Types.ttcn
@@ -1062,7 +1062,7 @@
 	}
 	template RSL_Message tr_RSL_UNITDATA_REQ(template RslChannelNr chan_nr,
 						 template RslLinkId link_id,
-						 template octetstring l3_info)
+						 template octetstring l3_info := ?)
 	modifies tr_RSL_DATA_REQ := {
 		msg_type := RSL_MT_UNIT_DATA_REQ
 	}
@@ -1077,7 +1077,7 @@
 	}
 	template RSL_Message tr_RSL_UNITDATA_IND(template RslChannelNr chan_nr,
 						 template RslLinkId link_id,
-						 template octetstring l3_info)
+						 template octetstring l3_info := ?)
 	modifies tr_RSL_DATA_IND := {
 		msg_type := RSL_MT_UNIT_DATA_IND
 	}