diff --git a/library/GSM_RR_Types.ttcn b/library/GSM_RR_Types.ttcn
index 457f0f543..627f78f33 100644
--- a/library/GSM_RR_Types.ttcn
+++ b/library/GSM_RR_Types.ttcn
@@ -587,7 +587,7 @@ module GSM_RR_Types {
 		TimingAdvance			timing_advance,
 		MobileAllocation		mobile_allocation,
 		/* TODO: starting time TLV */
-		IaRestOctets			rest_octets optional
+		IaRestOctets			rest_octets
 	} with { variant (chan_desc) "PRESENCE(ded_or_tbf.tbf = false)"
 		 variant (pkt_chan_desc) "PRESENCE(ded_or_tbf.tbf = true)" };
 
@@ -737,7 +737,14 @@ module GSM_RR_Types {
 				req_ref := f_compute_ReqRef(ra, fn),
 				timing_advance := ta,
 				mobile_allocation := ma,
-				rest_octets := omit
+				rest_octets := {
+					presence := '00'B, /* LL */
+					ll := {
+						/* Compressed INTER RAT HO INFO: shall not be used (L)
+						 * TODO: use variant "CSN.1 L/H" to avoid confusion. */
+						compressed_irat_ho_info_ind := '1'B
+					}
+				}
 			}
 		}
 	};
@@ -761,7 +768,7 @@ module GSM_RR_Types {
 				req_ref := tr_compute_ReqRef(ra, fn),
 				timing_advance := ta,
 				mobile_allocation := ma,
-				rest_octets := *
+				rest_octets := ?
 			}
 		}
 	};