Apt-Key add is executed every time

[martinseener]

Iam using the latest version and added this module like following for a squeeze machine (therefore the defined latest version available).
class { 'erlang': version => '1:16.b.2' }

Every time puppet runs (puppet 2.7.19-1puppetlabs2) the Apt-Key add is executed:
notice: /Stage[main]/Erlang::Repo::Apt/Apt::Source[erlang]/Apt::Key[Add key: D208507CA14F4FCA from Apt::Source erlang]/Exec[635832f17af02a891e7adc03b7789fc6a8ac8d39]/returns: executed successfully

but: erlang is otherwise correctly installed - no issues there - just the continous execution of the key-add thing which is not necessary