diff --git a/lib/rotp.rb b/lib/rotp.rb
index <HASH>..<HASH> 100644
--- a/lib/rotp.rb
+++ b/lib/rotp.rb
@@ -1,6 +1,7 @@
 require 'cgi'
 require 'uri'
 require 'securerandom'
+require 'openssl'
 require 'rotp/base32'
 require 'rotp/otp'
 require 'rotp/hotp'
Require Openssl to fix usage with ruby <I>.