Date_select throws an exception

Question

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

undefined method `map' for "translation missing: he.date.order":String <%= f.date_select :birthday %> 

I checked twice, and not only the locales for Hebrew and English are identical (by key), en.date.order is not included in English language files.

Where does this exception come from?

I am using Ruby 2 with Rails 4 .

Edit: Solution:

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