Fix after review

db/migrate/20170302112312_remove_deposit_datetime_from_dossiers.rb

@@ -1,8 +1,17 @@
 class RemoveDepositDatetimeFromDossiers < ActiveRecord::Migration[5.0]
   def change
+    remove_column :dossiers, :deposit_datetime, :datetime
+  end
+
+  def up
     Dossier.where.not(deposit_datetime: nil).each do |dossier|
       dossier.update(initiated_at: dossier.deposit_datetime)
     end
-    remove_column :dossiers, :deposit_datetime, :datetime
+  end
+
+  def down
+    Dossier.where.not(initiated_at: nil).each do |dossier|
+      dossier.update(deposit_datetime: dossier.initiated_at)
+    end
   end
 end