bundler provides gems not matching the current platform

Gemfile

# A sample Gemfile
source "https://rubygems.org"

gem "jrb-libsvm", git: 'git://github.com/sch1zo/jrb-libsvm.git',
    require: 'libsvm', platforms: :jruby
gem "rb-libsvm",  git: 'git://github.com/sch1zo/rb-libsvm.git', branch: 'custom_stuff',
    require: 'libsvm', platforms: :ruby

Gemfile.lock

GIT
  remote: git://github.com/sch1zo/jrb-libsvm.git
  revision: e7fcdb1333f86d51a3ae961d46b09381ce9c5eba
  specs:
    jrb-libsvm (0.0.1)

GIT
  remote: git://github.com/sch1zo/rb-libsvm.git
  revision: 1e22ffe052bb2b157b3c773443edcf46baeb3406
  branch: custom_stuff
  specs:
    rb-libsvm (1.0.11)

GEM
  remote: https://rubygems.org/
  specs:

PLATFORMS
  java
  ruby

DEPENDENCIES
  jrb-libsvm!
  rb-libsvm!

log

$> rvm --create use jruby-1.7.2@platforms-test
$> bundle install
Fetching git://github.com/sch1zo/jrb-libsvm.git
Fetching git://github.com/sch1zo/rb-libsvm.git
Fetching gem metadata from https://rubygems.org/.........
Fetching gem metadata from https://rubygems.org/..
Using jrb-libsvm (0.0.1) from git://github.com/sch1zo/jrb-libsvm.git (at master) 
Using bundler (1.2.3)
$> bundle list
Gems included by the bundle:
  * bundler (1.2.3)
  * jrb-libsvm (0.0.1 e7fcdb1)
$> bundle exec ruby platforms.rb
Run options: --seed 27834

# Running tests:

.....

Finished tests in 0.021000s, 238.0952 tests/s, 238.0952 assertions/s.

5 tests, 5 assertions, 0 failures, 0 errors, 0 skips


$> rvm --create use ruby-1.9.3-p362@platforms-test
$> bundle install
Fetching git://github.com/sch1zo/rb-libsvm.git
remote: Counting objects: 713, done.
remote: Compressing objects: 100% (357/357), done.
remote: Total 713 (delta 353), reused 656 (delta 297)
Receiving objects: 100% (713/713), 130.33 KiB, done.
Resolving deltas: 100% (353/353), done.
Fetching git://github.com/sch1zo/jrb-libsvm.git
remote: Counting objects: 109, done.
remote: Compressing objects: 100% (71/71), done.
remote: Total 109 (delta 41), reused 94 (delta 26)
Receiving objects: 100% (109/109), 150.00 KiB, done.
Resolving deltas: 100% (41/41), done.
Fetching gem metadata from https://rubygems.org/.........
Fetching gem metadata from https://rubygems.org/..
Using rb-libsvm (1.0.11) from git://github.com/sch1zo/rb-libsvm.git (at custom_stuff) with native extensions 
Using bundler (1.2.3)

$> bundle list
Gems included by the bundle:
  * bundler (1.2.3)
  * rb-libsvm (1.0.11 1e22ffe)
$> bundle exec ruby platforms.rb
/home/USER/.rvm/gems/ruby-1.9.3-p362@platforms-test/bundler/gems/jrb-libsvm-e7fcdb1333f8/lib/libsvm/version.rb:2: warning: already initialized constant VERSION
/home/USER/.rvm/gems/ruby-1.9.3-p362@platforms-test/bundler/gems/jrb-libsvm-e7fcdb1333f8/lib/libsvm.rb:2:in `require': cannot load such file -- java (LoadError)
        from /home/USER/.rvm/gems/ruby-1.9.3-p362@platforms-test/bundler/gems/jrb-libsvm-e7fcdb1333f8/lib/libsvm.rb:2:in `<top (required)>'
        from /home/USER/.rvm/gems/ruby-1.9.3-p362@global/gems/bundler-1.2.3/lib/bundler/runtime.rb:68:in `require'
        from /home/USER/.rvm/gems/ruby-1.9.3-p362@global/gems/bundler-1.2.3/lib/bundler/runtime.rb:68:in `block (2 levels) in require'
        from /home/USER/.rvm/gems/ruby-1.9.3-p362@global/gems/bundler-1.2.3/lib/bundler/runtime.rb:66:in `each'
        from /home/USER/.rvm/gems/ruby-1.9.3-p362@global/gems/bundler-1.2.3/lib/bundler/runtime.rb:66:in `block in require'
        from /home/USER/.rvm/gems/ruby-1.9.3-p362@global/gems/bundler-1.2.3/lib/bundler/runtime.rb:55:in `each'
        from /home/USER/.rvm/gems/ruby-1.9.3-p362@global/gems/bundler-1.2.3/lib/bundler/runtime.rb:55:in `require'
        from /home/USER/.rvm/gems/ruby-1.9.3-p362@global/gems/bundler-1.2.3/lib/bundler.rb:128:in `require'
        from platforms.rb:3:in `<main>'

#after removing line 4 and 5 from Gemfile

$> bundle install
Using rb-libsvm (1.0.11) from git://github.com/sch1zo/rb-libsvm.git (at custom_stuff) with native extensions 
Using bundler (1.2.3)
$> bundle exec ruby platforms.rb
Run options: --seed 11699

# Running tests:

.....

Finished tests in 0.000597s, 8369.1113 tests/s, 8369.1113 assertions/s.

5 tests, 5 assertions, 0 failures, 0 errors, 0 skips

platforms.rb

require 'bundler'
Bundler.setup
Bundler.require(:default)

require 'minitest/autorun'
describe 'platforms-test' do
  it 'should have a libsvm' do
    assert Object.const_defined?('Libsvm')
  end
  %w(Model Node SvmParameter Problem).each do |klass|
    it "should define the #{klass} class for libsvm" do
      assert Libsvm.const_defined?(klass)
    end
  end
end

both rb-libsvm and jrb-libsvm provide the same interface, one uses the C version and the other the Java version of the libary.

running the script in jruby works as expected, but when i switch to MRI bundler keeps loading the java version of the gem which obviously does not work

removing rubygems-bundler doesn't helps -> same results