This is an old, deprecated version of the Ruby PostgreSQL driver that hasn't been maintained or supported since early 2008. You should install/require 'pg' instead. If you need the 'postgres' gem for legacy code that can't be converted, you can still install it using an explicit version, like so: gem install postgres -v '0.7.9.2008.01.28' gem uninstall postgres -v '>0.7.9.2008.01.28' If you have any questions, the nice folks in the Google group can help: http://goo.gl/OjOPP / ruby-pg@googlegroups.com