FIX: extconf.rb:8:in `require’: no such file to load — mkmf (LoadError)

When i try to install fastthread in my new system,

gem install -v=1.0.7 fastthread

I got the following error,

/usr/bin/ruby1.8 extconf.rb
extconf.rb:8:in `require': no such file to load -- mkmf (LoadError)
from extconf.rb:8

The solution is to install ruby1.8-dev,

$ sudo apt-get install ruby1.8-dev

Now try.

Hope it should work fine for you as well.