diff --git a/lib/kosapi_client/entity/exam.rb b/lib/kosapi_client/entity/exam.rb
index 083982c..10dc02f 100644
--- a/lib/kosapi_client/entity/exam.rb
+++ b/lib/kosapi_client/entity/exam.rb
@@ -1,3 +1,5 @@
+require 'date'
+
 module KOSapiClient
   module Entity
     class Exam < BaseEntity