rake cannot find my tasks


I'm experiencing the following problem. I've just set up a rails
development environment on Gentoo Linux: ruby 1.8.4, gem 0.9 and the
latest rails package. Rails is generally working I can run my app, can
use with RadRails, etc.

But rake does not find my own tasks within lib/tasks folder. I can't
even see their names in tasks listed by rake -T command. What is funny
it works on my MacBook laptop (OS X 10.4.8, ruby and rails built from

What can be the difference between the two installation which makes rake fail?