diff --git a/library/SIP_Templates.ttcn b/library/SIP_Templates.ttcn
index e1c9ec6..e6e8b53 100644
--- a/library/SIP_Templates.ttcn
+++ b/library/SIP_Templates.ttcn
@@ -228,6 +228,16 @@
 	optionsTags := optionsTags
 }
 
+// [20.41 RFC2616 14.43]
+template (value) UserAgent ts_UserAgent(template (value) ServerVal_List userAgentBody := {}) := {
+	fieldName := USER_AGENT_E,
+	userAgentBody := userAgentBody
+}
+template (present) UserAgent tr_UserAgent(template (present) ServerVal_List userAgentBody := ?) := {
+	fieldName := USER_AGENT_E,
+	userAgentBody := userAgentBody
+}
+
 
 template (value) SipAddr ts_SipAddr(template (value) HostPort host_port,
 				    template (omit) UserInfo user_info := omit,
@@ -527,6 +537,7 @@
 		template (omit) Security_client security_client := omit,
 		template (omit) Security_server security_server := omit,
 		template (omit) Supported supported := omit,
+		template (omit) UserAgent userAgent := ts_UserAgent({ "osmo-ttcn3-hacks/0.23" }),
 		template (omit) WwwAuthenticate wwwAuthenticate := omit
 	) modifies ts_SIP_msgHeader_empty := {
 	allow := allow,
@@ -557,12 +568,7 @@
 		addressField := to_addr.addr,
 		toParams := to_addr.params
 	},
-	userAgent := {
-		fieldName := USER_AGENT_E,
-		userAgentBody := {
-			"osmo-ttcn3-hacks/0.23"
-		}
-	},
+	userAgent := userAgent,
 	via := via,
 	wwwAuthenticate := wwwAuthenticate
 }
@@ -582,6 +588,7 @@
 		template Security_client security_client := *,
 		template Security_server security_server := *,
 		template Supported supported := *,
+		template UserAgent userAgent := *,
 		template WwwAuthenticate wwwAuthenticate := *
 		) modifies t_SIP_msgHeader_any := {
 	allow := allow,
@@ -611,7 +618,7 @@
 		addressField := to_addr.addr,
 		toParams := to_addr.params
 	},
-	userAgent := *,
+	userAgent := userAgent,
 	via := via,
 	wwwAuthenticate := wwwAuthenticate
 }