diff --git a/lib/iso/iban.rb b/lib/iso/iban.rb
index <HASH>..<HASH> 100644
--- a/lib/iso/iban.rb
+++ b/lib/iso/iban.rb
@@ -2,6 +2,7 @@
 
 require 'iso/iban/specification'
 require 'iso/iban/version'
+require 'yaml'
 
 module ISO
Require yaml.