diff --git a/Library/Homebrew/extend/pathname.rb b/Library/Homebrew/extend/pathname.rb
index ef14801c58..6d45d0b77f 100644
--- a/Library/Homebrew/extend/pathname.rb
+++ b/Library/Homebrew/extend/pathname.rb
@@ -100,6 +100,7 @@ class Pathname
 
   # extended to support common double extensions
   def extname
+    return $1 if to_s =~ /(\.bottle\.tar\.gz)$/
     /(\.(tar|cpio)\.(gz|bz2|xz|Z))$/.match to_s
     return $1 if $1
     return File.extname(to_s)