diff --git a/app/decorators/invitation_decorator.rb b/app/decorators/invitation_decorator.rb
index e2b3f177a..0066ff9d3 100644
--- a/app/decorators/invitation_decorator.rb
+++ b/app/decorators/invitation_decorator.rb
@@ -3,9 +3,9 @@ class InvitationDecorator < Draper::Decorator
   decorates_association :proposal
 
   STATE_LABEL_MAP = {
-    Invitation::State::PENDING => 'label-default',
-    Invitation::State::DECLINED => 'label-danger',
-    Invitation::State::ACCEPTED => 'label-success'
+    Invitation.states[:pending] => 'label-default',
+    Invitation.states[:declined] => 'label-danger',
+    Invitation.states[:accepted] => 'label-success'
   }
 
   def decline_button(small: false)
diff --git a/app/models/concerns/invitable.rb b/app/models/concerns/invitable.rb
deleted file mode 100644
index 7b3a4a3c7..000000000
--- a/app/models/concerns/invitable.rb
+++ /dev/null
@@ -1,47 +0,0 @@
-# frozen_string_literal: true
-
-module Invitable
-  extend ActiveSupport::Concern
-
-  included do
-    module State
-      unless const_defined?(:DECLINED)
-        DECLINED = 'declined'
-        PENDING = 'pending'
-        ACCEPTED = 'accepted'
-      end
-    end
-
-    scope :pending, -> { where(state: State::PENDING) }
-    scope :declined, -> { where(state: State::DECLINED) }
-    scope :not_accepted, -> { where(state: [State::DECLINED, State::PENDING]) }
-
-    before_create :set_default_state
-    before_create :set_slug
-
-    validates :email, presence: true
-    validates_format_of :email, with: /@/
-  end
-
-  def decline
-    update(state: State::DECLINED)
-  end
-
-  def pending?
-    state == State::PENDING
-  end
-
-  def declined?
-    state == State::DECLINED
-  end
-
-  private
-
-  def set_slug
-    self.slug = Digest::SHA1.hexdigest([email, rand(1000)].map(&:to_s).join('-'))[0, 10]
-  end
-
-  def set_default_state
-    self.state = State::PENDING if state.nil?
-  end
-end
diff --git a/app/models/invitation.rb b/app/models/invitation.rb
index 49d763a3c..995616faf 100644
--- a/app/models/invitation.rb
+++ b/app/models/invitation.rb
@@ -1,17 +1,39 @@
 class Invitation < ApplicationRecord
-  include Invitable
+  enum :state, {pending: 'pending', accepted: 'accepted', declined: 'declined'}
 
   belongs_to :proposal
   belongs_to :user, optional: true
 
+  scope :not_accepted, -> { where(state: [:pending, :declined]) }
+
+  before_create :set_default_state
+  before_create :set_slug
+
+  validates :email, presence: true
+  validates_format_of :email, with: /@/
+
   def accept(user)
     transaction do
       self.user = user
-      self.state = State::ACCEPTED
+      self.state = :accepted
       proposal.speakers.create(user: user, event: proposal.event, skip_name_email_validation: true)
       save
     end
   end
+
+  def decline
+    update(state: :declined)
+  end
+
+  private
+
+  def set_slug
+    self.slug = Digest::SHA1.hexdigest([email, rand(1000)].map(&:to_s).join('-'))[0, 10]
+  end
+
+  def set_default_state
+    self.state = :pending if state.nil?
+  end
 end
 
 # == Schema Information
diff --git a/spec/models/invitation_spec.rb b/spec/models/invitation_spec.rb
index ddefd9c29..e979a0f90 100644
--- a/spec/models/invitation_spec.rb
+++ b/spec/models/invitation_spec.rb
@@ -19,14 +19,14 @@
     it "sets state as declined" do
       invitation = create(:invitation, state: nil, proposal: proposal, user: user)
       invitation.decline
-      expect(invitation.state).to eq(Invitation::State::DECLINED)
+      expect(invitation).to be_declined
     end
   end
 
   describe "#accept" do
     it "sets state as accepted" do
       invitation.accept(user)
-      expect(invitation.state).to eq(Invitation::State::ACCEPTED)
+      expect(invitation).to be_accepted
     end
 
     it "sets the user on the invitation" do
@@ -42,24 +42,24 @@
 
   describe "#pending?" do
     it "returns true if invitation is pending" do
-      invitation = create(:invitation, state: Invitation::State::PENDING, proposal: proposal, user: user)
+      invitation = create(:invitation, state: :pending, proposal: proposal, user: user)
       expect(invitation).to be_pending
     end
 
     it "returns false if invitation is not pending" do
-      invitation = create(:invitation, state: Invitation::State::ACCEPTED, proposal: proposal, user: user)
+      invitation = create(:invitation, state: :accepted, proposal: proposal, user: user)
       expect(invitation).to_not be_pending
     end
   end
 
   describe "#declined?" do
     it "returns true if invitation was declined" do
-      invitation = create(:invitation, state: Invitation::State::DECLINED, proposal: proposal, user: user)
+      invitation = create(:invitation, state: :declined, proposal: proposal, user: user)
       expect(invitation).to be_declined
     end
 
     it "returns false if invitation was not declined" do
-      invitation = create(:invitation, state: Invitation::State::ACCEPTED, proposal: proposal, user: user)
+      invitation = create(:invitation, state: :accepted, proposal: proposal, user: user)
       expect(invitation).to_not be_declined
     end
   end