lrelease produces too many messages

After I write "lrelease interface.pro", for the first translation, fet_ar.ts, I get a correct message. But then the messages for each new file contain also all the previous messages. So, if I have Arabic, Catalan, German, Greek: ar, ca, de, el, then el contains all messages for ar, ca and de (so I get n*(n-1)/2 messages for n languages).

You can replicate the bug if you download the sources version of my software ( lalescu.ro/liviu/fet/ ), enter directory src/interface/, and type "lrelease interface.pro".