Creating a Room with REST API Plugin

Hi I'm just trying to create a room via REST API Plugin 1.0.2 .

It seems to work fine the room given in the XML below is created just fine

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>

<chatRoom>

    <roomName>1234</roomName>

    <naturalName>1234@conference.local</naturalName>

    <description>Room 1234</description>

    <creationDate>2015-06-01T13:56:56.164+02:00</creationDate>

    <modificationDate>2015-06-01T13:56:56+02:00</modificationDate>

    <maxUsers>0</maxUsers>

    <persistent>true</persistent>

    <publicRoom>false</publicRoom>

    <registrationEnabled>true</registrationEnabled>

    <canAnyoneDiscoverJID>false</canAnyoneDiscoverJID>

    <canOccupantsChangeSubject>false</canOccupantsChangeSubject>

    <canOccupantsInvite>false</canOccupantsInvite>

    <canChangeNickname>false</canChangeNickname>

    <logEnabled>true</logEnabled>

    <loginRestrictedToNickname>false</loginRestrictedToNickname>

    <membersOnly>false</membersOnly>

    <moderated>false</moderated>

    <broadcastPresenceRoles/>

    <owners>

        <owner>admin@local</owner>

    </owners>

    <admins/>

    <members/>

    <outcasts/>

</chatRoom>

Problem is, once I try to join the room with a XIFF client, the client gets a "Declined" the RoomEvent "LOCKED_ERROR". When I edit the room once via the admin interface the room can be entered without a problem by the client.

Can you give me a hint which step is necessary in order to do this without the admin GUI.

Regards

Thomas