"go through door" raises Z::RuntimeError

[Billiam]

Testing with the hitchhiker's guide (after standing up, turning on lights), and zork 1 (immediately), the command

> go through door

raises the following exception:

dorothy/machine.rb:8:in `step': Error running program: Illegal first object for jin (Z::RuntimeError)
        from C:/Ruby193/lib/ruby/gems/1.9.1/bundler/gems/dorothy-d9580f5c2e90/lib/dorothy/machine.rb:8:in `block in run'
        from C:/Ruby193/lib/ruby/gems/1.9.1/bundler/gems/dorothy-d9580f5c2e90/lib/dorothy/machine.rb:7:in `loop'