diff --git a/33128/r17/TS33128Payloads.asn b/33128/r17/TS33128Payloads.asn
index e9aeccbfdefa3c19e3935652baf957ef038da891..4e3966feda7dbc34d8c0e7dbd976e65ae0d2f5da 100644
--- a/33128/r17/TS33128Payloads.asn
+++ b/33128/r17/TS33128Payloads.asn
@@ -2732,17 +2732,13 @@ PTCAccessPolicyFailure  ::= ENUMERATED
 -- ===============
 
 -- See clause 7.X.4.2.1 for details of this structure
-EncapsulatedSIPMessage ::= SEQUENCE
+IMSMessage ::= SEQUENCE
 {
-    sIPMessage            [1] OCTET STRING,
+    payload               [1] IMSPayload,
     sessionDirection      [2] SessionDirection,
-    iPSourceAddress       [3] IPAddress OPTIONAL,
-    iPDestinationAddress  [4] IPAddress OPTIONAL,
-    voIPRoamingIndication [5] VoIPRoamingIndication OPTIONAL,
-    location              [6] Location OPTIONAL,
-    headerOnlyIndication  [7] HeaderOnlyIndication OPTIONAL
+    voIPRoamingIndication [3] VoIPRoamingIndication OPTIONAL,
+    location              [6] Location OPTIONAL
 }
-
 -- See clause 7.X.4.2.3 for details of this structure
 StartOfInterceptionForActiveIMSSession ::= SEQUENCE
 {
@@ -2758,6 +2754,19 @@ StartOfInterceptionForActiveIMSSession ::= SEQUENCE
 -- IMS parameters
 -- ==============
 
+IMSPayload ::= CHOICE
+{
+    encapsulatedSIPMessage            [1] SIPMessage
+}
+
+SIPMessage ::= SEQUENCE
+{
+    iPSourceAddress       [1] IPAddress,
+    iPDestinationAddress  [2] IPAddress,
+    sIPContent            [3] OCTET STRING,
+    headerOnlyIndication  [4] HeaderOnlyIndication OPTIONAL
+}
+
 VoIPRoamingIndication ::= ENUMERATED
 {
     roamingLBO(1),