diff --git a/ttcn/Lib3GPP/NG_NAS/NG_NAS_TypeDefs.ttcn b/ttcn/Lib3GPP/NG_NAS/NG_NAS_TypeDefs.ttcn
index f8249d2d15dc4135dbd76301559821f69ef07c37..9267ec5cfead2f35de5e37ae6a7b4fc004e361dc 100644
--- a/ttcn/Lib3GPP/NG_NAS/NG_NAS_TypeDefs.ttcn
+++ b/ttcn/Lib3GPP/NG_NAS/NG_NAS_TypeDefs.ttcn
@@ -2495,14 +2495,13 @@ module NG_NAS_TypeDefs {
     B4_Type                     spare,
     B1_Type                     si16LLA,                    // @sic R5s201526 sic@
     B3_Type                     typeValue,
-    octetstring                 adressInfo length(4..12),
-    octetstring                 ipv6Address length(1..16) optional    /* Sep20 @sic R5s201387 Baseline Moving sic@ */
+    octetstring                 adressInfo length(4..12) optional,
+    octetstring                 ipv6Address length(16) optional    /* Sep20 @sic R5s201387 Baseline Moving sic@ */
   } with {
     variant "FIELDORDER(msb)";
     variant (iel) "LENGTHTO (spare, si16LLA, typeValue, adressInfo, ipv6Address)";
     variant (iel) "BYTEORDER(last)";
-    variant (adressInfo) "BYTEORDER(last)";
-    variant (ipv6Address) "BYTEORDER(last)";
+    variant (ipv6Address) "PRESENCE(si16LLA = '1'B)"
   };
 
   type record PDU_SessionType {                                 /* 24.501 cl. 9.11.4.11 */