diff --git a/devise_token_auth.gemspec b/devise_token_auth.gemspec
index f2da71b29..e89f4d796 100644
--- a/devise_token_auth.gemspec
+++ b/devise_token_auth.gemspec
@@ -23,7 +23,7 @@ Gem::Specification.new do |s|
   s.required_ruby_version = ">= 2.3.0"
 
   s.add_dependency 'rails', '>= 4.2.0', '< 8.2'
-  s.add_dependency 'devise', '> 3.5.2', '< 5'
+  s.add_dependency 'devise', '> 3.5.2', '< 6'
   s.add_dependency 'bcrypt', '~> 3.0'
 
   s.add_development_dependency 'appraisal'
diff --git a/test/lib/devise_token_auth/rails/custom_routes_test.rb b/test/lib/devise_token_auth/rails/custom_routes_test.rb
index 57ef71685..a480dea0f 100644
--- a/test/lib/devise_token_auth/rails/custom_routes_test.rb
+++ b/test/lib/devise_token_auth/rails/custom_routes_test.rb
@@ -7,11 +7,12 @@ class DeviseTokenAuth::CustomRoutesTest < ActiveSupport::TestCase
     Rails.application.reload_routes!
   end
   test 'custom controllers' do
-    class ActionDispatch::Routing::Mapper
-        include Mocha::ParameterMatchers
-    end
     Rails.application.routes.draw do
-      self.expects(:devise_for).with(
+      mapper = self
+      mapper.singleton_class.include(Mocha::API)
+      mapper.singleton_class.include(Mocha::ParameterMatchers)
+
+      mapper.expects(:devise_for).with(
         :users,
         has_entries(
           controllers: has_entries(