Issue #3607 has been updated by Roger Pack. I just ran into this, as well [1]. I suppose it's a bug that needs to be fixed within rubygems proper, then? The following fixed it for me, as a work around. C:\dev\ruby\downloads\rubygems>set RUBYOPT= C:\dev\ruby\downloads\rubygems>ruby --disable-gems setup.rb -r [1] http://gist.github.com/577354 ---------------------------------------- http://redmine.ruby-lang.org/issues/show/3607 ---------------------------------------- http://redmine.ruby-lang.org