diff --git a/library/SIP_Templates.ttcn b/library/SIP_Templates.ttcn
index 65f9d22..e2be94b 100644
--- a/library/SIP_Templates.ttcn
+++ b/library/SIP_Templates.ttcn
@@ -201,6 +201,16 @@
 }
 
 
+// [20.14]
+template (value) ContentLength ts_ContentLength(template (value) integer len := 0) := {
+	fieldName := CONTENT_LENGTH_E,
+	len := len
+}
+template (present) ContentLength tr_ContentLength(template (present) integer len := ?) := {
+	fieldName := CONTENT_LENGTH_E,
+	len := len
+}
+
 // [20.19]
 template (value) Expires ts_Expires(template (value) DeltaSec deltaSec := "7200") := {
 	fieldName := EXPIRES_E,
@@ -419,6 +429,16 @@
 	return ct;
 }
 
+private function f_ContentLength(template (omit) charstring body)
+return template (value) ContentLength {
+	/* rfc3261 20.14: "If no body is present in a message, then the
+	 * Content-Length header field value MUST be set to zero." */
+	if (istemplatekind(body, "omit")) {
+		return ts_ContentLength(0);
+	}
+	return ts_ContentLength(lengthof(body));
+}
+
 template (value) ContentType ts_CT_SDP := {
 	fieldName := CONTENT_TYPE_E,
 	mediaType := "application/sdp"
@@ -539,6 +559,7 @@
 		template (value) charstring method,
 		template (value) integer seq_nr,
 		template (value) Via via,
+		template (omit) ContentLength content_length := ts_ContentLength(0),
 		template (omit) ContentType content_type := omit,
 		template (omit)Authorization authorization := omit,
 		template (omit) Allow allow := ts_Allow(c_SIP_defaultMethods),
@@ -558,6 +579,7 @@
 		callid := call_id
 	},
 	contact := contact,
+	contentLength := content_length,
 	contentType := content_type,
 	cSeq := {
 		fieldName := CSEQ_E,
@@ -592,8 +614,9 @@
 		template Contact contact,
 		template (present) Via via := tr_Via_from(?),
 		template charstring method,
-		template ContentType content_type := *,
 		template integer seq_nr := ?,
+		template ContentLength content_length := *,
+		template ContentType content_type := *,
 		template Allow allow := *,
 		template Expires expires := *,
 		template Require require := *,
@@ -610,6 +633,7 @@
 		callid := call_id
 	},
 	contact := contact,
+	contentLength := content_length,
 	contentType := content_type,
 	cSeq := {
 		fieldName := CSEQ_E,
@@ -655,7 +679,8 @@
 	requestLine := ts_SIP_ReqLine(REGISTER_E, sip_url_host_port),
 	msgHeader := ts_SIP_msgh_std(call_id, from_addr, to_addr, contact,
 				     "REGISTER", seq_nr, via,
-				     f_ContentTypeOrOmit(ts_CT_SDP, body),
+				     content_length := f_ContentLength(body),
+				     content_type := f_ContentTypeOrOmit(ts_CT_SDP, body),
 				     authorization := authorization,
 				     expires := expires,
 				     require := require,
@@ -679,7 +704,7 @@
 		template charstring body := *) := {
 	requestLine := tr_SIP_ReqLine(REGISTER_E, sip_url_host_port),
 	msgHeader := tr_SIP_msgh_std(call_id, from_addr, to_addr, contact,
-				     via, "REGISTER", *, seq_nr,
+				     via, "REGISTER", seq_nr,
 				     expires := expires,
 				     require := require,
 				     security_client := security_client,
@@ -700,7 +725,8 @@
 	msgHeader := ts_SIP_msgh_std(call_id, from_addr, to_addr, contact,
 				     "INVITE", seq_nr,
 				     via,
-				     f_ContentTypeOrOmit(ts_CT_SDP, body)),
+				     content_length := f_ContentLength(body),
+				     content_type := f_ContentTypeOrOmit(ts_CT_SDP, body)),
 	messageBody := body,
 	payload := omit
 }
@@ -714,7 +740,7 @@
 	      template charstring body) := {
 	requestLine := tr_SIP_ReqLine(INVITE_E, uri),
 	msgHeader := tr_SIP_msgh_std(call_id, from_addr, to_addr, ?,
-				     via, "INVITE", *, seq_nr),
+				     via, "INVITE", seq_nr),
 	messageBody := body,
 	payload := omit
 }
@@ -728,7 +754,9 @@
 	   template (omit) charstring body) := {
 	requestLine := ts_SIP_ReqLine(BYE_E, to_addr.addr.nameAddr.addrSpec),
 	msgHeader := ts_SIP_msgh_std(call_id, from_addr, to_addr, omit, "BYE", seq_nr,
-				     via, f_ContentTypeOrOmit(ts_CT_SDP, body)),
+				     via,
+				     content_length := f_ContentLength(body),
+				     content_type := f_ContentTypeOrOmit(ts_CT_SDP, body)),
 	messageBody := body,
 	payload := omit
 }
@@ -743,7 +771,7 @@
 	   template charstring body := *) := {
 	requestLine := tr_SIP_ReqLine(BYE_E, uri),
 	msgHeader := tr_SIP_msgh_std(call_id, from_addr, to_addr, omit,
-				     via, "BYE", *, seq_nr),
+				     via, "BYE", seq_nr),
 	messageBody := body,
 	payload := omit
 }
@@ -761,7 +789,8 @@
 				     ts_Contact_SipAddr(from_addr),
 				     "ACK", seq_nr,
 				     via,
-				     f_ContentTypeOrOmit(ts_CT_SDP, body)),
+				     content_length := f_ContentLength(body),
+				     content_type := f_ContentTypeOrOmit(ts_CT_SDP, body)),
 	messageBody := body,
 	payload := omit
 }
@@ -776,7 +805,7 @@
 	requestLine := tr_SIP_ReqLine(ACK_E, uri),
 	msgHeader := tr_SIP_msgh_std(call_id, from_addr, to_addr, *,
 				     via,
-				     "ACK", *, seq_nr),
+				     "ACK", seq_nr),
 	messageBody := body,
 	payload := omit
 }
@@ -792,7 +821,7 @@
 	requestLine := tr_SIP_ReqLine(CANCEL_E, uri),
 	msgHeader := tr_SIP_msgh_std(call_id, from_addr, to_addr, *,
 				     via,
-				     "CANCEL", *, seq_nr),
+				     "CANCEL", seq_nr),
 	messageBody := body,
 	payload := omit
 }
@@ -809,7 +838,9 @@
 		template (omit) charstring body := omit) := {
 	statusLine := ts_SIP_StatusLine(status_code, reason),
 	msgHeader := ts_SIP_msgh_std(call_id, from_addr, to_addr, omit, method, seq_nr,
-				     via, f_ContentTypeOrOmit(ts_CT_SDP, body)),
+				     via,
+				     content_length := f_ContentLength(body),
+				     content_type := f_ContentTypeOrOmit(ts_CT_SDP, body)),
 	messageBody := body,
 	payload := omit
 }
@@ -825,7 +856,9 @@
 	template (omit) charstring body := omit) := {
 	statusLine := ts_SIP_StatusLine(100, "Trying"),
 	msgHeader := ts_SIP_msgh_std(call_id, from_addr, to_addr, omit, method, seq_nr,
-				     via, f_ContentTypeOrOmit(ts_CT_SDP, body)),
+				     via,
+				     content_length := f_ContentLength(body),
+				     content_type := f_ContentTypeOrOmit(ts_CT_SDP, body)),
 	messageBody := body,
 	payload := omit
 }
@@ -841,7 +874,9 @@
 	template (omit) charstring body := omit) := {
 	statusLine := ts_SIP_StatusLine(180, "Ringing"),
 	msgHeader := ts_SIP_msgh_std(call_id, from_addr, to_addr, omit, method, seq_nr,
-				     via, f_ContentTypeOrOmit(ts_CT_SDP, body)),
+				     via,
+				     content_length := f_ContentLength(body),
+				     content_type := f_ContentTypeOrOmit(ts_CT_SDP, body)),
 	messageBody := body,
 	payload := omit
 }
@@ -860,7 +895,7 @@
 	statusLine := tr_SIP_StatusLine(status_code, reason),
 	msgHeader := tr_SIP_msgh_std(call_id, from_addr, to_addr, contact,
 				     via,
-				     method, *, seq_nr),
+				     method, seq_nr),
 	messageBody := body,
 	payload := omit
 }
@@ -882,7 +917,7 @@
 	statusLine := tr_SIP_StatusLine(status_code, reason),
 	msgHeader := tr_SIP_msgh_std(call_id, from_addr, to_addr, contact,
 				     via,
-				     method, *, seq_nr,
+				     method, seq_nr,
 				     wwwAuthenticate := wwwAuthenticate),
 	messageBody := body,
 	payload := omit
@@ -903,7 +938,7 @@
 	statusLine := tr_SIP_StatusLine(status_code, reason),
 	msgHeader := tr_SIP_msgh_std(call_id, from_addr, to_addr, omit,
 				     via,
-				     method, *, seq_nr),
+				     method, seq_nr),
 	messageBody := body,
 	payload := omit
 }
@@ -923,7 +958,7 @@
 	statusLine := tr_SIP_StatusLine(status_code, reason),
 	msgHeader := tr_SIP_msgh_std(call_id, from_addr, to_addr, *,
 				     via,
-				     method, *, seq_nr),
+				     method, seq_nr),
 	messageBody := body,
 	payload := omit
 }