Why do I keep getting this ActiveRecord::AssociationTypeMismatch error?

I have two models that have a has_many association to the same object. I have a User, an Admin, and Visits.

Users has_many Visits Admins has_many Visits

Every time I create a Visit with a User it works, but when I do it with an Admin it gives me an error ActiveRecord::AssociationTypeMismatch.

The full error is this:User(#70282715553200) expected, got # which is an instance of Admin(#70282709528720)

def create
@visit = @service.visits.new(visit_params)

if user_signed_in?
  @visit.user = current_user
else
  @visit.user = current_admin
end

if @visit.save
  redirect_to service_visits_path(@service)
else
  redirect_to @services
end

end

class Admin < ApplicationRecord
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable, :trackable and 
:omniauthable
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :validatable

  has_many :visits, dependent: :destroy
  end

==============================

class User < ApplicationRecord
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable, :trackable and 
:omniauthable
  devise :database_authenticatable, :registerable,
     :recoverable, :rememberable, :validatable

  has_many :visits, dependent: :destroy
 end

==============================

class Visit < ApplicationRecord
  belongs_to :user
  belongs_to :admin
  belongs_to :service
end