diff --git a/lib/letter_opener.rb b/lib/letter_opener.rb
index d933218..8860dc2 100644
--- a/lib/letter_opener.rb
+++ b/lib/letter_opener.rb
@@ -1,6 +1,7 @@
 require "fileutils"
 require "digest/sha1"
 require "cgi"
+require "launchy"
 
 require "letter_opener/message"
 require "letter_opener/delivery_method"