Ruby on Rails 3 + Apache2 + Phusion Passenger: Bundler::GemNotFound exception

I'm trying to deploy a Rails app on an Apache2 server by using Phusion Passenger. While everything works well locally, I am getting the infamous "Bundler::GemNotFound" error while deploying:

Could not find abstract-1.0.0 in any of the sources (Bundler::GemNotFound)

All my gems are installed in my local home folder. Thus the passenger configuration lines from my Apache2 configuration file are as follows:

LoadModule passenger_module /home/regis/.gem/gems/passenger-3.0.7/ext/apache2/mod_passenger.so
PassengerRoot /home/regis/.gem/gems/passenger-3.0.7
PassengerRuby /usr/bin/ruby1.8

I understand you would need more information to analyse the issue at hand, but I have no idea on how to diagnose this further.