Apparently newgem has a dependency on rubigen. I'd expect that gem install newgem would auto-install its dependencies, then it. Thanks! -=r C:\dev\ruby_backtracer>gem install newgem ERROR: Error installing newgem: newgem requires rubigen (>= 1.5.1, runtime) C:\dev\ruby_backtracer>gem install rubigen Successfully installed rubigen-1.5.1 C:\dev\ruby_backtracer>gem install newgem Successfully installed newgem-1.2.3