mysql error after upgrading to Lucid Lynx

After I upgraded my Ubuntu machine from Karmic Koala to Lucid Lynx and running my ror app,
I get the following mysql error:

/usr/lib/ruby/gems/1.8/gems/mysql2-0.2.4/lib/mysql2/mysql2.so: libmysqlclient.so.15: cannot open shared object file: No such file or directory - /usr/lib/ruby/gems/1.8/gems/mysql2-0.2.4/lib/mysql2/mysql2.so (LoadError)

Running this command fixes the error:

$ sudo apt-get install ruby-dev