Delete Node (PubSub) fails in 4.1.0-alpha7-SNAPSHOT

There seems to be a problem with node deletion in 4.1.0-alpha7-SNAPSHOT. PubSubManager#deleteNode creates the following message:

Request:

<iq to="pubsub.ec-xmpp" id="2GAeW-75" type="set">

  <pubsub xmlns="http://jabber.org/protocol/pubsub">

    <delete node="2e92d38c-9e90-47f6-8e26-330d25ebe96b"/>

  </pubsub>

</iq>

Response:

<iq to="xmpp.proxy@ec-xmpp/pc377" from="pubsub.ec-xmpp" id="2GAeW-75" type="error">

  <error type="modify">

    <bad-request xmlns="urn:ietf:params:xml:ns:xmpp-stanzas"/>

  </error>

</iq>

I think the namespace for the delete request must be "http://jabber.org/protocol/pubsub#owner". I don't know if the "from" attribute is required. Please have a look to the standard: XEP-0060: Publish-Subscribe