merge_gem 'neography' break bundle with iron worker

I'm trying to deploy a Iron worker (cf https://iron.io) with few gems. When i'm adding neography and trying to deploy the worker, initialisation is crashing. I don't know if it's an issue neography side or iron side (I opened a ticket neography side too cf. https://github.com/maxdemarzi/neography/issues/175).

Already tried the gem 'zip-zip' and read these topics

https://github.com/rubyzip/rubyzip/issues/90 https://github.com/maxdemarzi/neography/pull/109

graph.worker

# define the runtime language
runtime 'ruby'

# worker name
name "GraphWorker"

# stack
stack 'ruby-2.1'

# remote Build
remote

# gem dependencies
merge_gem 'activerecord', '3.2.18'
merge_gem 'pg'
merge_gem 'koala'
merge_gem 'neography'

# includes files
dir 'app/models'

# initiliazer
file 'config/initializers/neography.rb'

# exec is the file that will be executed:
exec 'app/workers/my_worker.rb'

logs

I, [2014-05-23T23:26:45.750586 #15]  INFO -- IronWorkerNG: Found workerfile with path='GraphWorker.worker'
I, [2014-05-23T23:26:45.751070 #15]  INFO -- IronWorkerNG: Adding ruby gem dependency with name='activerecord' and version='3.2.18'
I, [2014-05-23T23:26:45.751120 #15]  INFO -- IronWorkerNG: Adding ruby gem dependency with name='pg' and version='>= 0'
I, [2014-05-23T23:26:45.751194 #15]  INFO -- IronWorkerNG: Adding ruby gem dependency with name='neography' and version='>= 0'
I, [2014-05-23T23:26:45.751234 #15]  INFO -- IronWorkerNG: Merging dir with path='__build__/models' and dest=''
I, [2014-05-23T23:26:45.751278 #15]  INFO -- IronWorkerNG: Merging file with path='__build__/neography.rb' and dest=''
I, [2014-05-23T23:26:45.751327 #15]  INFO -- IronWorkerNG: Detected exec with path='__build__/load_new_user_graph_connections_worker.rb' and args='{}'
/mnt/task/__gems__/gems/bundler-1.6.2/lib/bundler/runtime.rb:34:in `block in setup': You have already activated rubyzip 0.9.9, but your Gemfile requires rubyzip 1.1.3. Prepending `bundle exec` to your command may solve this. (Gem::LoadError)
    from /mnt/task/__gems__/gems/bundler-1.6.2/lib/bundler/runtime.rb:19:in `setup'
    from /mnt/task/__gems__/gems/bundler-1.6.2/lib/bundler.rb:120:in `setup'
    from /mnt/task/__gems__/gems/bundler-1.6.2/lib/bundler/setup.rb:17:in `<top (required)>'
    from /usr/local/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require'
    from /usr/local/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require'
    from /mnt/task/__builder__.rb:45:in `<top (required)>'
    from /usr/local/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require'
    from /usr/local/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require'
    from __runner__.rb:213:in `<main>'
Fetching gem metadata from http://rubygems.org/........
Fetching additional metadata from http://rubygems.org/..
Resolving dependencies...
Installing rake 10.3.2
Installing i18n 0.6.9
Installing multi_json 1.10.1
Installing activesupport 3.2.18
Installing builder 3.0.4
Installing activemodel 3.2.18
Installing arel 3.0.3
Installing tzinfo 0.3.39
Installing activerecord 3.2.18
Installing excon 0.33.0
Using json 1.8.1
Installing os 0.9.6
Installing neography 1.5.0
Installing pg 0.17.1
Using bundler 1.6.2
Your bundle is complete!
It was installed into ./bundle

iron-io / issues

merge_gem 'neography' break bundle with iron worker #99

graph.worker

logs