diff --git a/Library/Homebrew/dev-cmd/extract.rb b/Library/Homebrew/dev-cmd/extract.rb
index 0fecd1502d..64218b879f 100644
--- a/Library/Homebrew/dev-cmd/extract.rb
+++ b/Library/Homebrew/dev-cmd/extract.rb
@@ -142,7 +142,7 @@ module Homebrew
 
     # The class name has to be renamed to match the new filename,
     # e.g. Foo version 1.2.3 becomes FooAT123 and resides in Foo@1.2.3.rb.
-    class_name = name.capitalize
+    class_name = Formulary.class_s(name.to_s)
     versioned_name = Formulary.class_s("#{class_name}@#{version}")
     result.gsub!("class #{class_name} < Formula", "class #{versioned_name} < Formula")