Plone:behavior not recognized

In my efforts to modularize a quite big Plone product, I created a package which, for a start, should provide a behavior (so far a simple schema with one field, and a method to this for search indexes). However, despite I believe I followed the instructions here, with my behaviors.zcml activated, Zope won't start:

zope.configuration.xmlconfig.ZopeXMLConfigurationError: File "/opt/zope/instances/NAME/parts/instance/etc/site.zcml", line 16.2-16.23
    ZopeXMLConfigurationError: File "/opt/zope/eggs/Products.CMFPlone-4.3.3-py2.7.egg/Products/CMFPlone/configure.zcml", line 98.4-102.10
    ZopeXMLConfigurationError: File "/opt/zope/instances/NAME/src/visaplan.subportal/visaplan/subportal/configure.zcml", line 13.4-13.37
    ZopeXMLConfigurationError: File "/opt/zope/instances/NAME/src/visaplan.subportal/visaplan/subportal/behaviors.zcml", line 9.4
    ConfigurationError: ('Unknown directive', u'http://namespaces.zope.org/plone', u'behavior')

This comes unexpected, since the <plone:behavior> element is prepended by <include package="plone.behavior" file="meta.zcml" /> which should provide the behavior directive, right?

My (so far quite simple) package is on GitHub, with a tracker issue as well.

My development setup is based on Plone 4.3.14 so far; updating to Plone 4.3.15 didn't change the situation. The plone.behavior version is 1.2.0.

Any idea what is missing, someone? Is the documentation incomplete? Any special version requirements?

Thank you!

Try this:

<?xml version="1.0"?>
<configure xmlns="http://namespaces.zope.org/zope"
           xmlns:five="http://namespaces.zope.org/five"
           xmlns:plone="http://namespaces.plone.org/plone"
           xmlns:i18n="http://namespaces.zope.org/i18n"
           i18n_domain="visaplan.subportal">

    <include package="plone.behavior" file="meta.zcml" />

    <plone:behavior
        title="Subportal support"
        description="Fields and methods for support of Unitracc's subportals"
        provides=".behaviors.ISubportalSupport"
        marker=".behaviors.ISubportalSupport"
        factory=".behaviors.SubportalSupport"
        />
</configure>

PS: I usually use 'for=' and not 'marker', so I am not sure about that line.

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