diff --git a/app/models/pool.rb b/app/models/pool.rb
index c100fba90..6e126b3a4 100644
--- a/app/models/pool.rb
+++ b/app/models/pool.rb
@@ -168,7 +168,7 @@ class Pool < ActiveRecord::Base
   end
 
   def page_number(post_id)
-    post_id_array.find_index(post_id) + 1
+    post_id_array.find_index(post_id).to_i + 1
   end
 
   def deletable_by?(user)