diff --git a/library/DIAMETER_Emulation.ttcn b/library/DIAMETER_Emulation.ttcn
index fad44c3..6dd44b3 100644
--- a/library/DIAMETER_Emulation.ttcn
+++ b/library/DIAMETER_Emulation.ttcn
@@ -216,7 +216,16 @@
 
 	imsi_avp := f_DIAMETER_get_avp(pdu, c_AVP_Code_BASE_NONE_User_Name);
 	if (istemplatekind(imsi_avp, "omit")) {
-		return omit;
+		var template (omit) AVP sid_avp;
+		sid_avp := f_DIAMETER_get_avp(pdu, c_AVP_Code_DCC_NONE_Subscription_Id);
+		if (istemplatekind(sid_avp, "omit")) {
+			return omit;
+		}
+		var AVP_Grouped grp := valueof(sid_avp.avp_data.avp_DCC_NONE_Subscription_Id);
+		if (not match(grp[0], tr_SubcrIdType(END_USER_IMSI))) {
+			return omit;
+		}
+		return str2hex(oct2char(grp[1].avp.avp_data.avp_DCC_NONE_Subscription_Id_Data));
 	} else {
 		var octetstring imsi_oct := valueof(imsi_avp.avp_data.avp_BASE_NONE_User_Name);
 		return str2hex(oct2char(imsi_oct));