diff --git a/db/migrate/20130331182719_add_pixiv_id_to_posts.rb b/db/migrate/20130331182719_add_pixiv_id_to_posts.rb
index 473333aa0..416e6e9d3 100644
--- a/db/migrate/20130331182719_add_pixiv_id_to_posts.rb
+++ b/db/migrate/20130331182719_add_pixiv_id_to_posts.rb
@@ -1,6 +1,7 @@
 class AddPixivIdToPosts < ActiveRecord::Migration
   def up
     execute "set statement_timeout = 0"
+    remove_index :posts, :pixiv_id
     add_column :posts, :pixiv_id, :integer
     execute "create index index_posts_on_pixiv_id on posts (pixiv_id) where pixiv_id is not null"
   end