Why can’t I install the sqlite gem?

sudo gem install sqlite3-ruby
Building native extensions. This could take a while...
ERROR: Error installing sqlite3-ruby:
ERROR: Failed to build gem native extension.

/usr/bin/ruby extconf.rb install sqlite3-ruby
can't find header files for ruby.

Gem files will remain installed in /usr/lib/ruby/gems/1.8/gems/sqlite3-ruby-1.2.4 for inspection.
Results logged to /usr/lib/ruby/gems/1.8/gems/sqlite3-ruby-1.2.4/ext/sqlite3_api/gem_make.out

solution:
apt-get install libsqlite3-ruby