gem install: Failed to build gem native extension (can't find header files)

I am using Fedora 14 and I have MySQL and MySQL server 5.1.42 installed and running. Now I tried to do this as root user: gem install mysql But I get this error: Building native extensions. This could take a while... ERROR: Error installing mysql: ERROR: Failed to build gem native extension. /usr/bin/ruby extconf.rb mkmf.rb can't find header files for ruby at /usr/lib/ruby/ruby.h Gem files will remain installed in /usr/lib/ruby/gems/1.8/gems/mysql-2.8.1 for inspection. Results logged to /usr/lib/ruby/gems/1.8/gems/mysql-2.8.1/ext/mysql_api/gem_make.out What's wrong here? In installed ruby 1.8.7. and the latest rubygems 1.3.7.