Rails 5: validation of acceptance for a checkbox - ruby-on-rails

Question

I have a sign-up form with some nested fields, and inside this form I have added a checkbox for the terms of service.
I'm trying to validate when the checkbox is checked or not and return an error if not.
validates_acceptance_of :agreement, :allow_nil => true, :accept => true, :on => :create
I do have a boolean column that is set to default inside the accounts table.
add_column :accounts, :agreement, :boolean, default: false
Also, I have added the :agreement to the permitted controller params.
This is the form:
<%= form_for(resource, as: resource_name, url: registration_path(resource_name)) do |f| %>
<div class="centerList">
<div id="error_explanation">
<%= devise_error_messages! %></div>
</div>
<div class="form-group">
<span class="asterisk_input"></span>
<%= f.email_field :email, autofocus: true, placeholder: "email", :class=>"form-control" %>
</div>
<div class="form-group">
<span class="asterisk_input"></span>
<%= f.password_field :password, placeholder: "password", autocomplete: "off", :class=>"form-control" %>
</div>
<div class="form-group">
<span class="asterisk_input"></span>
<%= f.password_field :password_confirmation, placeholder: "confirm password", autocomplete: "off", :class=>"form-control" %>
</div>
<%= f.fields_for :account do |form| %>
<div class="form-group">
<span class="asterisk_input"></span>
<%= form.text_field :street, placeholder: "street", :class=>"form-control" %>
</div>
<div class="form-group">
<span class="asterisk_input"></span>
<%= form.text_field :city, placeholder: "city", :class=>"form-control" %>
</div>
<div class="form-group">
<span class="asterisk_input"></span>
<%= form.text_field :state, placeholder: "state", :class=>"form-control" %>
</div>
<div class="form-group">
<span class="asterisk_input"></span>
<%= form.text_field :zip_code, placeholder: "zip code", :class=>"form-control" %>
</div>
<div class="form-group">
<span class="asterisk_input"></span>
<%= form.country_select :country, ["US"], {}, { :class => "form-control", :id=>"sign-frm-input" } %>
</div>
<div class="form-group">
<%= form.check_box :agreement %> I agree to the <%= link_to 'Terms', term_path(:id=>1) %>.
</div>
<% end %>
<div class="form-group">
<%= f.submit "Sign up", :class=>'btn btn-primary' %>
<% end %>
But it returns the form error agreement must be accepted even if I do accept it. Any ideas what I might be missing ohere!

Answer 1

Try: validates :agreement, acceptance: {accept: true} , on: :create,
allow_nil: false
You don't want to :allow_nil => true if you're validating for acceptance.

Answer 2

You can change your model validations and test it.
validates :agreement, inclusion: {in: [true]}
or you can use other validation
validates :agreement, acceptance: { accept: true }