ruby-on-rails - date_select throws an exception

Question

When the application locale is set to :he, the following auto-generated code throws an exception:

undefined method `map' for "translation missing: he.date.order":String

<%= f.date_select :birthday %>

I double checked and not only the locales for Hebrew and English are identical (key-wise), the English locale files does not include en.date.order.

Where can this exception stem from?

I'm using Ruby 2 with Rails 4.

Edit: Solution:

he:
  date: #Throws an exception otherwise.
    order:
      - "year"
      - "month"
      - "day"