diff --git a/library/SIP_Templates.ttcn b/library/SIP_Templates.ttcn
index ce5998b..26f7ea8 100644
--- a/library/SIP_Templates.ttcn
+++ b/library/SIP_Templates.ttcn
@@ -245,6 +245,12 @@
 	fromParams := fromParams
 }
 
+// [20.23]
+template (value) MinExpires ts_MinExpires(template (value) DeltaSec deltaSec := "800000") := {
+	fieldName := MIN_EXPIRES_E,
+	deltaSec := deltaSec
+}
+
 // [RFC3455 5.4] + 3GPP 24.229 V8.7.0
 template (present) Access_net_spec tr_Access_net_spec(template (present) charstring access_type := ?,
 						      template SemicolonParam_List access_info := *) := {
@@ -685,6 +691,7 @@
 		template (omit)Authorization authorization := omit,
 		template (omit) Allow allow := ts_Allow(c_SIP_defaultMethods),
 		template (omit) Expires expires := omit,
+		template (omit) MinExpires minExpires := omit,
 		template (omit) P_Associated_Uri p_associated_uri := omit,
 		template (omit) RAck rack := omit,
 		template (omit) Require require := omit,
@@ -712,6 +719,7 @@
 	},
 	expires := expires,
 	fromField := from_addr,
+	minExpires := minExpires,
 	p_associated_uri := p_associated_uri,
 	rack := rack,
 	require := require,
@@ -1152,6 +1160,34 @@
 	payload := omit
 }
 
+/* Tx 423 Interval Too Brief */
+template (value) PDU_SIP_Response
+ts_SIP_Response_423_Interval_Too_Brief(
+	template (value) CallidString call_id,
+	template (value) From from_addr,
+	template (value) To to_addr,
+	Via via,
+	integer seq_nr,
+	charstring method := "REGISTER",
+	template (omit) Allow allow := omit,
+	template (value) MinExpires minExpires := ts_MinExpires(),
+	template (omit) Server server := omit,
+	template (omit) Supported supported := omit,
+	template (omit) UserAgent userAgent := omit) := {
+	statusLine := ts_SIP_StatusLine(423, "Interval Too Brief"),
+	msgHeader := ts_SIP_msgh_std(call_id, from_addr, to_addr, omit, method, seq_nr,
+				     via,
+				     content_length := f_ContentLength(omit),
+				     content_type := f_ContentTypeOrOmit(ts_CT_SDP, omit),
+				     allow := allow,
+				     minExpires := minExpires,
+				     server := server,
+				     supported := supported,
+				     userAgent := userAgent),
+	messageBody := omit,
+	payload := omit
+}
+
 template (present) PDU_SIP_Response
 tr_SIP_Response(template CallidString call_id,
 		template From from_addr,