diff --git a/dlls/webservices/msg.c b/dlls/webservices/msg.c
index 2bac6e036fb..9a196222513 100644
--- a/dlls/webservices/msg.c
+++ b/dlls/webservices/msg.c
@@ -349,6 +349,11 @@ static HRESULT get_addr_namespace( WS_ADDRESSING_VERSION ver, WS_XML_STRING *str
         str->length = sizeof(ns_addr_1_0)/sizeof(ns_addr_1_0[0]) - 1;
         return S_OK;
 
+    case WS_ADDRESSING_VERSION_TRANSPORT:
+        str->bytes  = NULL;
+        str->length = 0;
+        return S_OK;
+
     default:
         ERR( "unhandled addressing version %u\n", ver );
         return E_NOTIMPL;
@@ -409,14 +414,18 @@ static HRESULT write_envelope_start( struct msg *msg, WS_XML_WRITER *writer )
     if ((hr = get_addr_namespace( msg->version_addr, &ns_addr )) != S_OK) return hr;
 
     if ((hr = WsWriteStartElement( writer, &prefix_s, &envelope, &ns_env, NULL )) != S_OK) return hr;
-    if ((hr = WsWriteXmlnsAttribute( writer, &prefix_a, &ns_addr, FALSE, NULL )) != S_OK) return hr;
+    if (msg->version_addr < WS_ADDRESSING_VERSION_TRANSPORT &&
+        (hr = WsWriteXmlnsAttribute( writer, &prefix_a, &ns_addr, FALSE, NULL )) != S_OK) return hr;
     if ((hr = WsWriteStartElement( writer, &prefix_s, &header, &ns_env, NULL )) != S_OK) return hr;
-    if ((hr = WsWriteStartElement( writer, &prefix_a, &msgid, &ns_addr, NULL )) != S_OK) return hr;
 
-    urn.text.textType = WS_XML_TEXT_TYPE_UNIQUE_ID;
-    memcpy( &urn.value, &msg->id, sizeof(msg->id) );
-    if ((hr = WsWriteText( writer, &urn.text, NULL )) != S_OK) return hr;
-    if ((hr = WsWriteEndElement( writer, NULL )) != S_OK) return hr; /* </a:MessageID> */
+    if (msg->version_addr < WS_ADDRESSING_VERSION_TRANSPORT)
+    {
+        if ((hr = WsWriteStartElement( writer, &prefix_a, &msgid, &ns_addr, NULL )) != S_OK) return hr;
+        urn.text.textType = WS_XML_TEXT_TYPE_UNIQUE_ID;
+        memcpy( &urn.value, &msg->id, sizeof(msg->id) );
+        if ((hr = WsWriteText( writer, &urn.text, NULL )) != S_OK) return hr;
+        if ((hr = WsWriteEndElement( writer, NULL )) != S_OK) return hr; /* </a:MessageID> */
+    }
 
     for (i = 0; i < msg->header_count; i++)
     {
diff --git a/dlls/webservices/tests/msg.c b/dlls/webservices/tests/msg.c
index a42d36972af..5a0e8b2a587 100644
--- a/dlls/webservices/tests/msg.c
+++ b/dlls/webservices/tests/msg.c
@@ -339,6 +339,8 @@ static void test_WsWriteEnvelopeStart(void)
         "<a:MessageID>urn:uuid:00000000-0000-0000-0000-000000000000</a:MessageID>"
         "<a:ReplyTo><a:Address>http://schemas.xmlsoap.org/ws/2004/08/addressing/role/anonymous</a:Address>"
         "</a:ReplyTo></s:Header><s:Body/></s:Envelope>";
+    static const char expected3[] =
+        "<s:Envelope xmlns:s=\"http://schemas.xmlsoap.org/soap/envelope/\"><s:Header/><s:Body/></s:Envelope>";
     HRESULT hr;
     WS_MESSAGE *msg;
     WS_XML_WRITER *writer;
@@ -375,6 +377,21 @@ static void test_WsWriteEnvelopeStart(void)
     hr = WsGetMessageProperty( msg, WS_MESSAGE_PROPERTY_STATE, &state, sizeof(state), NULL );
     ok( hr == S_OK, "got %08x\n", hr );
     ok( state == WS_MESSAGE_STATE_WRITING, "got %u\n", state );
+    WsFreeMessage( msg );
+
+    hr = WsCreateMessage( WS_ENVELOPE_VERSION_SOAP_1_1, WS_ADDRESSING_VERSION_TRANSPORT, NULL, 0, &msg,
+                          NULL );
+    ok( hr == S_OK, "got %08x\n", hr );
+
+    hr = WsInitializeMessage( msg, WS_REQUEST_MESSAGE, NULL, NULL );
+    ok( hr == S_OK, "got %08x\n", hr );
+
+    hr = set_output( writer );
+    ok( hr == S_OK, "got %08x\n", hr );
+
+    hr = WsWriteEnvelopeStart( msg, writer, NULL, NULL, NULL );
+    ok( hr == S_OK, "got %08x\n", hr );
+    check_output_header( msg, expected3, -1, 0, 0, __LINE__ );
 
     WsFreeMessage( msg );
     WsFreeWriter( writer );