diff --git a/lib/generators/invitation/install/templates/invitation.rb b/lib/generators/invitation/install/templates/invitation.rb
index 2ec7075..d0adf5e 100644
--- a/lib/generators/invitation/install/templates/invitation.rb
+++ b/lib/generators/invitation/install/templates/invitation.rb
@@ -1,5 +1,5 @@
 Invitation.configure do |config|
-  # config.user_model = ::User
+  # config.user_model = '::User'
   # config.user_registration_url = ->(params) { Rails.application.routes.url_helpers.sign_up_url(params) }
   # config.mailer_sender = 'reply@example.com'
   # config.routes = true
diff --git a/lib/invitation/configuration.rb b/lib/invitation/configuration.rb
index b426529..24f345e 100644
--- a/lib/invitation/configuration.rb
+++ b/lib/invitation/configuration.rb
@@ -54,19 +54,23 @@ class Configuration
     attr_accessor :case_sensitive_email
 
     def initialize
-      @user_model = ::User if defined?(::User)
+      @user_model = '::User' #if defined?(::User)
       @user_registration_url = ->(params) { Rails.application.routes.url_helpers.sign_up_url(params) }
       @mailer_sender = 'reply@example.com'
       @routes = true
       @case_sensitive_email = true
     end
 
+    def user_model
+      @user_model.constantize
+    end
+
     def user_model_class_name
-      @user_model.name.to_s
+      user_model.name.to_s
     end
 
     def user_model_instance_var
-      '@' + @user_model.name.demodulize.underscore
+      '@' + user_model.name.demodulize.underscore
     end
 
     # @return [Boolean] are Invitation's built-in routes enabled?
diff --git a/spec/dummy/config/initializers/invitation.rb b/spec/dummy/config/initializers/invitation.rb
index 768f629..6e1d4ae 100644
--- a/spec/dummy/config/initializers/invitation.rb
+++ b/spec/dummy/config/initializers/invitation.rb
@@ -1,4 +1,4 @@
 Invitation.configure do |config|
-  config.user_model = User
+  config.user_model = 'User'
   config.user_registration_url = ->(params) { 'this_is_a_fake_user_registration_url' }
 end
diff --git a/spec/models/configuration_spec.rb b/spec/models/configuration_spec.rb
index 770e547..207be26 100644
--- a/spec/models/configuration_spec.rb
+++ b/spec/models/configuration_spec.rb
@@ -23,7 +23,7 @@ class Profile
 
     before(:each) do
       @conf = Invitation::Configuration.new
-      @conf.user_model = Gug::Profile
+      @conf.user_model = 'Gug::Profile'
     end
 
     it 'has a user model class name' do
@@ -41,7 +41,7 @@ class UserProfile; extend ActiveModel::Naming end
 
     it 'has a user model instance variable name' do
       @conf = Invitation::Configuration.new
-      @conf.user_model = UserProfile
+      @conf.user_model = 'UserProfile'
       expect(@conf.user_model_instance_var).to eq('@user_profile')
     end
   end