gems and custom_require problem for ruby(1.9.2dev)/rubygems(1.3.6)installed in $HOME

[Nikolai Lugovoi]

I installed ruby 1.9.2dev (2010-03-17 trunk 26961) [i686-linux] in my
$HOME dir using configure --prefix=$HOME && make install
also i set PATH=$HOME/bin:$PATH

Then, I tried to run rake test on edge rails version, having required
gems installed via "bundle install"

gem list shows them installed

But, "rake test", complained that it cannot find required rubygems,
like: activerecord/test/cases/helper.rb:12:in `require': no such file
to load -- mocha

As a workaround, it started only with following RUBYOPT options:

RUBYOPT="-rubygems -rrubygems/custom_require" rake test

What am I missing that causes the problem?

Also, here is sample IRB session showing the issue:
$ irb
irb(main):001:0> RUBY_VERSION
=> "1.9.2"
irb(main):002:0> Gem::VERSION
=> "1.3.6"
irb(main):003:0> require 'mocha'
LoadError: no such file to load -- mocha
from (irb):3:in `require'
from (irb):3
from /home/nlugovoi/bin/irb:12:in `<main>'
irb(main):004:0> require 'rubygems'
=> false
irb(main):005:0> require 'mocha'
LoadError: no such file to load -- mocha
from (irb):5:in `require'
from (irb):5
from /home/nlugovoi/bin/irb:12:in `<main>'
irb(main):006:0> require 'rubygems/custom_require'
=> true
irb(main):007:0> require 'mocha'
=> true
irb(main):008:0> Gem.path
=> ["/home/nlugovoi/.gem/ruby/1.9.1", "/home/nlugovoi/lib/ruby/gems/1.9.1"]