zeus: zeus v0.15.10: undefined method `invoke' for RSpec::Core::Runner::Class

Just installed new zeus from rubygems and ran into this issue:

$ zeus rspec spec/
/Users/noice/.rbenv/versions/2.0.0-p598/lib/ruby/gems/2.0.0/gems/zeus-0.15.10/lib/zeus/rails.rb:207:in `test': undefined method `invoke' for RSpec::Core::Runner:Class (NoMethodError)
        from /Users/noice/.rbenv/versions/2.0.0-p598/lib/ruby/gems/2.0.0/gems/zeus-0.15.10/lib/zeus.rb:147:in `block in command'
        from /Users/noice/.rbenv/versions/2.0.0-p598/lib/ruby/gems/2.0.0/gems/zeus-0.15.10/lib/zeus.rb:134:in `fork'
        from /Users/noice/.rbenv/versions/2.0.0-p598/lib/ruby/gems/2.0.0/gems/zeus-0.15.10/lib/zeus.rb:134:in `command'
        from /Users/noice/.rbenv/versions/2.0.0-p598/lib/ruby/gems/2.0.0/gems/zeus-0.15.10/lib/zeus.rb:50:in `go'
        from -e:1:in `<main>'

Zeus itself starts just fine.

ruby 2.0.0p598
$ bundle list|egrep "\* (rails|rake)"
  * rails (4.0.10)
  * rails-observers (0.1.2)
  * rake (10.4.2)
$ bundle list|grep rspec
  * guard-rspec (4.2.0)
  * rspec (2.14.1)
  * rspec-core (2.14.7)
  * rspec-expectations (2.14.4)
  * rspec-mocks (2.14.4)
  * rspec-rails (2.14.0)

Downgraded to my previously installed zeus 0.15.4 and that still works correctly.