Uploading a specific pair of files to rails 4.0.4/rbx 2.2.6/nginx 1.5.12/passenger enterprise 4.0.40 fails

gistfile1.txt

App 11159 stderr: [ 2014-04-04 22:31:47.7216 11313/0x2320c(Worker 4) utils.rb:52 ]: *** Exception NoMethodError in Rack application object (undefined method `-' on nil:NilClass.) (process 11313, thread 0x2320c(Worker 4)):
App 11159 stderr: 	from kernel/delta/kernel.rb:78:in `- (method_missing)'
App 11159 stderr: 	from kernel/common/string.rb:1997:in `[]='
App 11159 stderr: 	from kernel/common/string.rb:1332:in `slice!'
App 11159 stderr: 	from /home/deploy/cogs/shared/bundle/rbx/2.1/gems/rack-1.5.2/lib/rack/multipart/parser.rb:113:in `get_current_head_and_filename_and_content_type_and_name_and_body'
App 11159 stderr: 	from /home/deploy/cogs/shared/bundle/rbx/2.1/gems/rack-1.5.2/lib/rack/multipart/parser.rb:19:in `parse'
App 11159 stderr: 	from kernel/common/kernel.rb:460:in `loop'
App 11159 stderr: 	from /home/deploy/cogs/shared/bundle/rbx/2.1/gems/rack-1.5.2/lib/rack/multipart/parser.rb:17:in `parse'
App 11159 stderr: 	from /home/deploy/cogs/shared/bundle/rbx/2.1/gems/rack-1.5.2/lib/rack/multipart.rb:25:in `parse_multipart'
App 11159 stderr: 	from /home/deploy/cogs/shared/bundle/rbx/2.1/gems/rack-1.5.2/lib/rack/request.rb:377:in `parse_multipart'
App 11159 stderr: 	from /home/deploy/cogs/shared/bundle/rbx/2.1/gems/rack-1.5.2/lib/rack/request.rb:203:in `POST'
App 11159 stderr: 	from /home/deploy/cogs/shared/bundle/rbx/2.1/gems/rack-1.5.2/lib/rack/methodoverride.rb:26:in `method_override'
App 11159 stderr: 	from /home/deploy/cogs/shared/bundle/rbx/2.1/gems/rack-1.5.2/lib/rack/methodoverride.rb:14:in `call'
App 11159 stderr: 	from /home/deploy/cogs/shared/bundle/rbx/2.1/gems/rack-1.5.2/lib/rack/runtime.rb:17:in `call'
App 11159 stderr: 	from /home/deploy/cogs/shared/bundle/rbx/2.1/gems/rack-1.5.2/lib/rack/sendfile.rb:112:in `call'
App 11159 stderr: 	from /home/deploy/cogs/shared/bundle/rbx/2.1/gems/actionpack-4.0.4/lib/action_dispatch/middleware/ssl.rb:24:in `call'
App 11159 stderr: 	from /home/deploy/cogs/shared/bundle/rbx/2.1/gems/railties-4.0.4/lib/rails/engine.rb:511:in `call'
App 11159 stderr: 	from /home/deploy/cogs/shared/bundle/rbx/2.1/gems/railties-4.0.4/lib/rails/application.rb:97:in `call'
App 11159 stderr: 	from /usr/local/rvm/gems/rbx-2.2.6/gems/passenger-enterprise-server-4.0.40/lib/phusion_passenger/rack/thread_handler_extension.rb:58:in `process_request'
App 11159 stderr: 	from /usr/local/rvm/gems/rbx-2.2.6/gems/passenger-enterprise-server-4.0.40/lib/phusion_passenger/request_handler/thread_handler.rb:126:in `accept_and_process_next_request'
App 11159 stderr: 	from /usr/local/rvm/gems/rbx-2.2.6/gems/passenger-enterprise-server-4.0.40/lib/phusion_passenger/request_handler/thread_handler.rb:94:in `main_loop'
App 11159 stderr: 	from /usr/local/rvm/gems/rbx-2.2.6/gems/passenger-enterprise-server-4.0.40/lib/phusion_passenger/request_handler.rb:471:in `start_threads'
App 11159 stderr: 	from kernel/bootstrap/proc.rb:20:in `call'
App 11159 stderr: 	from kernel/bootstrap/thread.rb:391:in `__run__'

I can replicate locally with the same setup, but only happens in production, not development.

Okay it happens in development too, but still always on the passenger setup. Doesn't happen with Puma.

Happens with Passenger Standalone to.