Issue with Translation.translate() helper

Hi guys,
I just ran into an issue with the Translation.translate() helper in my fusion files.
Making a long story short, if I use it in this form:

Translation.translate([translation.id],[translation.fallback.value], [arguments], [Source.Filename], [My.Package])

everything seems to work just fine but if I try to use it like this:

Translation.translate([translation.id])

it returns the ID as is wthout translating it.

What am I missing here?

Thanks,
Nicola