diff --git a/Library/Homebrew/brew.h.rb b/Library/Homebrew/brew.h.rb
index d8c64b6fa5..ed80ecc221 100644
--- a/Library/Homebrew/brew.h.rb
+++ b/Library/Homebrew/brew.h.rb
@@ -114,6 +114,8 @@ ENV.libxml2 in your formula's install function.
 
 #{force_text}
     EOS
+  when /rubygem/
+    raise "Sorry RubyGems comes with OS X so we don't package it.\n\n#{force_text}"
   end unless ARGV.force?
 
   __make url, name