Heroku installation

Got encoding error while installing heroku gem on Windows:

> gem install heroku
...
Installing RDoc documentation for rest-client-1.6.7...
ERROR: While generating documentation for rest-client-1.6.7
... MESSAGE: error generating C:/Ruby193/lib/ruby/gems/1.9.1/doc/rest-client-1.6.7/rdoc/README_rdoc.html: incompatible encoding regexp match (UTF-8 regexp with IBM866 string) (Encoding::CompatibilityError)
... RDOC args: --op C:/Ruby193/lib/ruby/gems/1.9.1/doc/rest-client-1.6.7/rdoc lib README.rdoc history.md --title rest-client-1.6.7 Documentation --quiet

Found a solution here:

> set RDOCOPT="--encoding=UTF-8"
> gem install heroku
Successfully installed heroku-2.18.1
1 gem installed
Installing ri documentation for heroku-2.18.1...
Installing RDoc documentation for heroku-2.18.1...


Update.
I've also taken that while installing rails on Mac:
$ sudo gem install rails
Installing RDoc documentation for i18n-0.6.0...
ERROR: While generating documentation for i18n-0.6.0
... MESSAGE: error generating I18n.html: incompatible encoding regexp match (UTF-8 regexp with ASCII-8BIT string) (Encoding::CompatibilityError)
... RDOC args: --op /usr/local/lib/ruby/gems/1.9.1/doc/i18n-0.6.0/rdoc lib --title i18n-0.6.0 Documentation --quiet

All installed successfully after:
$ export RDOCOPT="--encoding=UTF-8"