I always get an error when I try the following command:

sudo gem install krb5-auth

Building native extensions.  This could take a while...
ERROR:  Error installing krb5-auth:
	ERROR: Failed to build gem native extension.

        /usr/bin/ruby1.8 extconf.rb
checking for main() in -lc... yes
checking for krb5_init_context() in -lkrb5... no
creating Makefile

make
gcc -I. -I. -I/usr/lib/ruby/1.8/x86_64-linux -I. -D_FORTIFY_SOURCE=2  -D_FORTIFY_SOURCE=2 -fPIC -fno-strict-aliasing
-g -g -O2  -fPIC   -c ruby_krb5_auth.c
ruby_krb5_auth.c:24:18: fatal error: krb5.h: No such file or directory
compilation terminated.
make: *** [ruby_krb5_auth.o] Error 1


Gem files will remain installed in /var/lib/gems/1.8/gems/krb5-auth-0.7 for inspection.
Results logged to /var/lib/gems/1.8/gems/krb5-auth-0.7/ext/gem_make.out


Ubuntu 12.04.2 amd64

I have also tried downloading .tgz archive, but 'sudo gem install pkg/krb5-auth-0.7.gem' gives me the same error.