Rails 5 Select Not Validating - ruby-on-rails

Question

I have an issue where a validation is suddenly not working. The field is a select box, and it's not setting the value. So when I try to submit the form, it says that Payee can't be blank. This is a 1 to 1 relationship between Expense and Payee. What happened? Do you see any issues here?
The field in question. It's in a helper but I've tried putting it back into the form with no luck.
def expense_payee_id_field(f)
f.select :payee_id, Payee.all.collect { |p| [p.display_name, p.id] }, { prompt: "Choose Payee"},{class:"fluid ui dropdown"}
end
The form:
<%= form_for #expense, html: { :class => "ui form segment" }, :remote => true do |f|%>
<div class="field">
<%= f.label :date%>
<div class="ui small input">
<%= f.date_field :date %>
</div>
</div>
<div class="field">
<%= f.label :amount %>
<div class="ui small input">
<%= f.text_field :amount %>
</div>
</div>
<div class="field">
<%= f.label :check_number %>
<div class="ui small input">
<%= f.text_field :check_number %>
</div>
</div>
<div class="field">
<%= f.label :payee %>
<div class="ui input">
<%= expense_payee_id_field(f)%>
</div>
</div>
<%= f.submit class: "ui blue button" %>
<% end %>
My models:
expense.rb
class Expense < ApplicationRecord
has_one :payee
monetize :amount_cents
has_many :expense_expense_categories, inverse_of: :expense
has_many :expense_categories, through: :expense_expense_categories, :dependent => :destroy
accepts_nested_attributes_for :expense_expense_categories,:allow_destroy => true
validates_associated :expense_expense_categories
validates :date, presence: true
validates_numericality_of :amount, presence: true, greater_than: 0
validates :expense_expense_category_ids, presence: true
validates_presence_of :payee_id
end
payee.rb
class Payee < ApplicationRecord
belongs_to :expense
validate :company_or_name
def full_name
[first_name, last_name].join(" ")
end
def display_name
if company.blank?
full_name
else
company
end
end
private
def company_or_name
if company.blank? && first_name.blank?
errors[:base] << "You must specify company or name"
end
end
end