diff --git a/Library/Homebrew/cmd/options.rb b/Library/Homebrew/cmd/options.rb
index 530c881677..040c4a74b8 100644
--- a/Library/Homebrew/cmd/options.rb
+++ b/Library/Homebrew/cmd/options.rb
@@ -32,7 +32,8 @@ module Homebrew extend self
 
   def dump_options_for_formula f
     f.build.each do |k,v|
-      puts "--"+k
+      k.prepend "--" unless k.start_with? "--"
+      puts k
       puts "\t"+v
     end
   end