diff --git a/library/DIAMETER_ts29_273_Templates.ttcn b/library/DIAMETER_ts29_273_Templates.ttcn
index 71f6cfc..e3a6c2f 100644
--- a/library/DIAMETER_ts29_273_Templates.ttcn
+++ b/library/DIAMETER_ts29_273_Templates.ttcn
@@ -205,7 +205,7 @@
 
  /* TS 29.273 9.2.2.5.1 AA-Request (AAR) */
 template (value) PDU_DIAMETER
-ts_DIA_S6b_AAR(template (value) hexstring imsi,
+ts_DIA_S6b_AAR(template (value) charstring username_nai,
 	       template (value) MIPv6_NONE_MIP6_Feature_Vector mip6_feat_vec,
 	       template (value) charstring apn,
 	       template (value) octetstring sess_id := c_def_sess_id,
@@ -227,7 +227,7 @@
 			ts_AVP_OriginRealm(orig_realm),
 			ts_AVP_DestinationRealm(dest_realm),
 			ts_AVP_AuthRequestType(AUTHORIZE_ONLY),
-			ts_AVP_UserNameImsi(valueof(imsi)),
+			ts_AVP_UserName(char2oct(valueof(username_nai))),
 			ts_AVP_MIP6FeatureVector(mip6_feat_vec),
 			ts_AVP_ServiceSelection(valueof(apn))
 			/* TODO: Lots other optional */