ruby on rails - how do I get bundler to stop adding java to the end of the gem name -

i working on project i'm using sinatra server inside small application i'm writing. use jruby 9.0.4.0 in shop i'm working. install works fine when do:

gem install mygem-1.0.0.gem 

and shows me

successfully installed sinatra-1.4.7 installed mygem-1.0.0 

when add gem our existing project via gemfile

gem mygem, 1.0.0 

and perform bundle install, get:

bundler not find compatible versions gem "sinatra":    in gemfile:     mygem(= 1.0.0) java resolved 1.0.0, depends on       sinatra java not find gem 'sinatra java', required gem 'mygem'............ 

why can work fine when gem install, when add gem gemfile cries not being able find compatible gem. why looking 'sinatra java' , how can push 'sinatra'

note: have verified application works using gem install method, not ideal method.

edit:

this how gem specified in gemspec

spec.add_runtime_dependency 'sinatra' 

edit2:

the gemfile has

source 'https://rubygems.org'  # specify gem's dependencies in cucumber_distributed.gemspec gemspec 

bundler adds platform end of gem name indicate running on different platform specified in gem's gemspec.

see issue: confusing error message when gemspec has different platform what's in gemfile.lock

this can solved adding platform specification in gemfile, eg:

gem mygem, 1.0.0, platforms: :ruby