diff --git a/app/models/book.rb b/app/models/book.rb
index 438031b..cf1e96b 100644
--- a/app/models/book.rb
+++ b/app/models/book.rb
@@ -1,6 +1,6 @@
 class Book < ApplicationRecord
   validates :title, presence: true
-  #validates :year_published, numericality: { only_integer: true }
+  validates :year_published, numericality: { only_integer: true }
 
   def old?
     return false unless year_published