installing plone tries to install plone 5.0a2

Hi there
for a migration project I try to install plone 3.3.6.
Now buildout tries to install plone 5.0a2 ..

and eventually buildout breaks with the following message:

While:
   Installing instance.
Error: There is a version conflict.
We already have: plone.protect 1.1
but Products.CMFPlone 5.0a2 requires 'plone.protect>=3.0.0a1'.

how can I prevent buildout to install plone 5.0a2

thanks for your help
robert


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