using dfsbuild to build a debian from scratch

I want to create my own debian distribution using dfsbuild (v 1.0.2.0) but i got the error:

Project:/home/adrian# dfsbuild -c /etc/dfsbuild/dfs.cfg -w /home/adrian/dfs/
[dfs/INFO] Welcome to dfsbuild. Image architecture: "i386"
[dfs/INFO] Using working directory /home/adrian/dfs
[dfs/INFO] Using library directory /usr/lib/dfsbuild
[dfs/INFO] Running.
[dfs/INFO] Mirroring process starting.
[dfs/INFO] Running cdebootstrap for testing
E: Couldn't download Release!
[dfs/CRITICAL] Exception: user error (("cdebootstrap",["-q","-d","testing","/home/adrian/dfs/target","http://mirror.cujae.edu.cu/debian"]): exited with code 1)
dfsbuild: user error (("cdebootstrap",["-q","-d","testing","/home/adrian/dfs/target","http://mirror.cujae.edu.cu/debian"]): exited with code 1)

I checked the file release in http://mirror.cujae.edu.cu/debian/dists/lenny/Release, and it is apparently fine.