diff --git a/Library/Homebrew/extend/pathname.rb b/Library/Homebrew/extend/pathname.rb
index 33ccbfd1c3..49adae2d15 100644
--- a/Library/Homebrew/extend/pathname.rb
+++ b/Library/Homebrew/extend/pathname.rb
@@ -7,7 +7,7 @@ require 'metafiles'
 class Pathname
   include MachO
 
-  BOTTLE_EXTNAME_RX = /(\.[-a-z0-9_]+\.bottle\.(\d+\.)?tar\.gz)$/
+  BOTTLE_EXTNAME_RX = /(\.[a-z0-9_]+\.bottle\.(\d+\.)?tar\.gz)$/
 
   def install *sources
     sources.each do |src|