outdated says gems are outdated when they are not

[indirect]

[andre ~/sw/gems/bundler-testcases/i912]$ cat Gemfile
source :rubygems

gem 'rdoc', '>= 2.5.10'
gem 'horo', '>= 1.0.2'
[andre ~/sw/gems/bundler-testcases/i912]$ cat Gemfile.lock
GEM
  remote: http://rubygems.org/
  specs:
    horo (1.0.3)
      rdoc (>= 2.5)
    rdoc (3.6.1)

PLATFORMS
  ruby

DEPENDENCIES
  horo (>= 1.0.2)
  rdoc (>= 2.5.10)
[andre ~/sw/gems/bundler-testcases/i912]$ dbundle outdated
Fetching source index for http://rubygems.org/
rdoc (3.6.1 > 2.5.11)