diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index faae9299..fc4bedea 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -13,6 +13,7 @@ jobs:
           - gemfiles/Gemfile-rails-7-2
           - gemfiles/Gemfile-rails-8-0
         ruby:
+          - '4.0'
           - '3.4'
           - '3.3'
           - '3.2'
diff --git a/CHANGELOG.md b/CHANGELOG.md
index eb99ca57..f477421b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -24,7 +24,7 @@
 * enhancements
   * Add Rails 8 support.
     - Routes are lazy-loaded by default in test and development environments now so Devise loads them before `Devise.mappings` call. [#5728](https://github.com/heartcombo/devise/pull/5728)
-  * Add Ruby 3.4 support.
+  * Add Ruby 3.4 and 4.0 support.
   * Reenable Mongoid test suite across all Rails 7+ versions, to ensure we continue supporting it. Changes to dirty tracking to support Mongoid 8.0+. [#5568](https://github.com/heartcombo/devise/pull/5568)
   * Password length validator is changed from
 
diff --git a/Gemfile b/Gemfile
index 0f18834e..3fc8499f 100644
--- a/Gemfile
+++ b/Gemfile
@@ -14,12 +14,14 @@ gem "rails-controller-testing"
 gem "responders", "~> 3.1"
 
 group :test do
+  gem "minitest", "< 6"
   gem "mocha", "~> 2.1", require: false
   gem "omniauth-facebook"
   gem "omniauth-openid"
   gem "rexml"
   gem "timecop"
   gem "webrat"
+  gem "ostruct"
 end
 
 platforms :ruby do
diff --git a/Gemfile.lock b/Gemfile.lock
index 1aec779e..2d6b0ccd 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,9 +1,9 @@
 GIT
   remote: https://github.com/mongodb/mongoid.git
-  revision: 1d3deaa9d028176988205f541ee588621030662a
+  revision: 4dcdaddea5d88a819c7c0d98ea0e994e13f515fe
   branch: 9.0-stable
   specs:
-    mongoid (9.0.8)
+    mongoid (9.0.9)
       activemodel (>= 5.1, < 8.2, != 7.0.0)
       concurrent-ruby (>= 1.0.5, < 2.0)
       mongo (>= 2.18.0, < 3.0.0)
@@ -23,29 +23,29 @@ GEM
   specs:
     action_text-trix (2.1.15)
       railties
-    actioncable (8.1.0)
-      actionpack (= 8.1.0)
-      activesupport (= 8.1.0)
+    actioncable (8.1.1)
+      actionpack (= 8.1.1)
+      activesupport (= 8.1.1)
       nio4r (~> 2.0)
       websocket-driver (>= 0.6.1)
       zeitwerk (~> 2.6)
-    actionmailbox (8.1.0)
-      actionpack (= 8.1.0)
-      activejob (= 8.1.0)
-      activerecord (= 8.1.0)
-      activestorage (= 8.1.0)
-      activesupport (= 8.1.0)
+    actionmailbox (8.1.1)
+      actionpack (= 8.1.1)
+      activejob (= 8.1.1)
+      activerecord (= 8.1.1)
+      activestorage (= 8.1.1)
+      activesupport (= 8.1.1)
       mail (>= 2.8.0)
-    actionmailer (8.1.0)
-      actionpack (= 8.1.0)
-      actionview (= 8.1.0)
-      activejob (= 8.1.0)
-      activesupport (= 8.1.0)
+    actionmailer (8.1.1)
+      actionpack (= 8.1.1)
+      actionview (= 8.1.1)
+      activejob (= 8.1.1)
+      activesupport (= 8.1.1)
       mail (>= 2.8.0)
       rails-dom-testing (~> 2.2)
-    actionpack (8.1.0)
-      actionview (= 8.1.0)
-      activesupport (= 8.1.0)
+    actionpack (8.1.1)
+      actionview (= 8.1.1)
+      activesupport (= 8.1.1)
       nokogiri (>= 1.8.5)
       rack (>= 2.2.4)
       rack-session (>= 1.0.1)
@@ -53,36 +53,36 @@ GEM
       rails-dom-testing (~> 2.2)
       rails-html-sanitizer (~> 1.6)
       useragent (~> 0.16)
-    actiontext (8.1.0)
+    actiontext (8.1.1)
       action_text-trix (~> 2.1.15)
-      actionpack (= 8.1.0)
-      activerecord (= 8.1.0)
-      activestorage (= 8.1.0)
-      activesupport (= 8.1.0)
+      actionpack (= 8.1.1)
+      activerecord (= 8.1.1)
+      activestorage (= 8.1.1)
+      activesupport (= 8.1.1)
       globalid (>= 0.6.0)
       nokogiri (>= 1.8.5)
-    actionview (8.1.0)
-      activesupport (= 8.1.0)
+    actionview (8.1.1)
+      activesupport (= 8.1.1)
       builder (~> 3.1)
       erubi (~> 1.11)
       rails-dom-testing (~> 2.2)
       rails-html-sanitizer (~> 1.6)
-    activejob (8.1.0)
-      activesupport (= 8.1.0)
+    activejob (8.1.1)
+      activesupport (= 8.1.1)
       globalid (>= 0.3.6)
-    activemodel (8.1.0)
-      activesupport (= 8.1.0)
-    activerecord (8.1.0)
-      activemodel (= 8.1.0)
-      activesupport (= 8.1.0)
+    activemodel (8.1.1)
+      activesupport (= 8.1.1)
+    activerecord (8.1.1)
+      activemodel (= 8.1.1)
+      activesupport (= 8.1.1)
       timeout (>= 0.4.0)
-    activestorage (8.1.0)
-      actionpack (= 8.1.0)
-      activejob (= 8.1.0)
-      activerecord (= 8.1.0)
-      activesupport (= 8.1.0)
+    activestorage (8.1.1)
+      actionpack (= 8.1.1)
+      activejob (= 8.1.1)
+      activerecord (= 8.1.1)
+      activesupport (= 8.1.1)
       marcel (~> 1.0)
-    activesupport (8.1.0)
+    activesupport (8.1.1)
       base64
       bigdecimal
       concurrent-ruby (~> 1.0, >= 1.3.1)
@@ -97,37 +97,38 @@ GEM
       uri (>= 0.13.1)
     base64 (0.3.0)
     bcrypt (3.1.20)
-    bigdecimal (3.3.1)
+    bigdecimal (4.0.1)
     bson (5.2.0)
     builder (3.3.0)
-    concurrent-ruby (1.3.5)
-    connection_pool (2.5.4)
+    concurrent-ruby (1.3.6)
+    connection_pool (3.0.2)
     crass (1.0.6)
-    date (3.4.1)
+    date (3.5.1)
     drb (2.2.3)
-    erb (5.1.1)
+    erb (6.0.1)
     erubi (1.13.1)
     faraday (2.14.0)
       faraday-net_http (>= 2.0, < 3.5)
       json
       logger
-    faraday-net_http (3.4.1)
-      net-http (>= 0.5.0)
+    faraday-net_http (3.4.2)
+      net-http (~> 0.5)
     globalid (1.3.0)
       activesupport (>= 6.1)
-    hashie (5.0.0)
-    i18n (1.14.7)
+    hashie (5.1.0)
+      logger
+    i18n (1.14.8)
       concurrent-ruby (~> 1.0)
-    io-console (0.8.1)
-    irb (1.15.2)
+    io-console (0.8.2)
+    irb (1.16.0)
       pp (>= 0.6.0)
       rdoc (>= 4.0.0)
       reline (>= 0.4.2)
-    json (2.15.1)
+    json (2.18.0)
     jwt (3.1.2)
       base64
     logger (1.7.0)
-    loofah (2.24.1)
+    loofah (2.25.0)
       crass (~> 1.0.2)
       nokogiri (>= 1.12.0)
     mail (2.9.0)
@@ -139,17 +140,17 @@ GEM
     marcel (1.1.0)
     mini_mime (1.1.5)
     mini_portile2 (2.8.9)
-    minitest (5.26.0)
-    mocha (2.7.1)
+    minitest (5.27.0)
+    mocha (2.8.2)
       ruby2_keywords (>= 0.0.5)
-    mongo (2.21.3)
+    mongo (2.22.0)
       base64
       bson (>= 4.14.1, < 6.0.0)
-    multi_xml (0.7.2)
-      bigdecimal (~> 3.1)
-    net-http (0.6.0)
-      uri
-    net-imap (0.5.12)
+    multi_xml (0.8.0)
+      bigdecimal (>= 3.1, < 5)
+    net-http (0.9.1)
+      uri (>= 0.11.1)
+    net-imap (0.6.2)
       date
       net-protocol
     net-pop (0.1.2)
@@ -158,11 +159,11 @@ GEM
       timeout
     net-smtp (0.5.1)
       net-protocol
-    nio4r (2.7.4)
-    nokogiri (1.18.10)
+    nio4r (2.7.5)
+    nokogiri (1.19.0)
       mini_portile2 (~> 2.8.2)
       racc (~> 1.4)
-    oauth2 (2.0.17)
+    oauth2 (2.0.18)
       faraday (>= 0.17.3, < 4.0)
       jwt (>= 1.0, < 4.0)
       logger (~> 1.2)
@@ -178,8 +179,8 @@ GEM
     omniauth-facebook (10.0.0)
       bigdecimal
       omniauth-oauth2 (>= 1.2, < 3)
-    omniauth-oauth2 (1.8.0)
-      oauth2 (>= 1.4, < 3)
+    omniauth-oauth2 (1.9.0)
+      oauth2 (>= 2.0.2, < 3)
       omniauth (~> 2.0)
     omniauth-openid (2.0.2)
       omniauth (>= 1.1)
@@ -187,14 +188,15 @@ GEM
       ruby-openid (~> 2.1, >= 2.1.8)
       version_gem (~> 1.1, >= 1.1.8)
     orm_adapter (0.5.0)
+    ostruct (0.6.3)
     pp (0.6.3)
       prettyprint
     prettyprint (0.2.0)
-    psych (5.2.6)
+    psych (5.3.1)
       date
       stringio
     racc (1.8.1)
-    rack (3.2.3)
+    rack (3.2.4)
     rack-openid (1.4.2)
       rack (>= 1.1.0)
       ruby-openid (>= 2.1.8)
@@ -207,22 +209,22 @@ GEM
       rack (>= 3.0.0)
     rack-test (2.2.0)
       rack (>= 1.3)
-    rackup (2.2.1)
+    rackup (2.3.1)
       rack (>= 3)
-    rails (8.1.0)
-      actioncable (= 8.1.0)
-      actionmailbox (= 8.1.0)
-      actionmailer (= 8.1.0)
-      actionpack (= 8.1.0)
-      actiontext (= 8.1.0)
-      actionview (= 8.1.0)
-      activejob (= 8.1.0)
-      activemodel (= 8.1.0)
-      activerecord (= 8.1.0)
-      activestorage (= 8.1.0)
-      activesupport (= 8.1.0)
+    rails (8.1.1)
+      actioncable (= 8.1.1)
+      actionmailbox (= 8.1.1)
+      actionmailer (= 8.1.1)
+      actionpack (= 8.1.1)
+      actiontext (= 8.1.1)
+      actionview (= 8.1.1)
+      activejob (= 8.1.1)
+      activemodel (= 8.1.1)
+      activerecord (= 8.1.1)
+      activestorage (= 8.1.1)
+      activesupport (= 8.1.1)
       bundler (>= 1.15.0)
-      railties (= 8.1.0)
+      railties (= 8.1.1)
     rails-controller-testing (1.0.5)
       actionpack (>= 5.0.1.rc1)
       actionview (>= 5.0.1.rc1)
@@ -234,21 +236,21 @@ GEM
     rails-html-sanitizer (1.6.2)
       loofah (~> 2.21)
       nokogiri (>= 1.15.7, != 1.16.7, != 1.16.6, != 1.16.5, != 1.16.4, != 1.16.3, != 1.16.2, != 1.16.1, != 1.16.0.rc1, != 1.16.0)
-    railties (8.1.0)
-      actionpack (= 8.1.0)
-      activesupport (= 8.1.0)
+    railties (8.1.1)
+      actionpack (= 8.1.1)
+      activesupport (= 8.1.1)
       irb (~> 1.13)
       rackup (>= 1.0.0)
       rake (>= 12.2)
       thor (~> 1.0, >= 1.2.2)
       tsort (>= 0.2)
       zeitwerk (~> 2.6)
-    rake (13.3.0)
-    rdoc (6.15.0)
+    rake (13.3.1)
+    rdoc (7.0.3)
       erb
       psych (>= 4.0.0)
       tsort
-    reline (0.6.2)
+    reline (0.6.3)
       io-console (~> 0.5)
     responders (3.2.0)
       actionpack (>= 7.0)
@@ -260,16 +262,16 @@ GEM
     snaky_hash (2.0.3)
       hashie (>= 0.1.0, < 6)
       version_gem (>= 1.1.8, < 3)
-    sqlite3 (2.7.4)
+    sqlite3 (2.9.0)
       mini_portile2 (~> 2.8.0)
-    stringio (3.1.7)
+    stringio (3.2.0)
     thor (1.4.0)
     timecop (0.9.10)
-    timeout (0.4.3)
+    timeout (0.6.0)
     tsort (0.2.0)
     tzinfo (2.0.6)
       concurrent-ruby (~> 1.0)
-    uri (1.0.4)
+    uri (1.1.1)
     useragent (0.16.11)
     version_gem (1.1.9)
     warden (1.2.9)
@@ -282,19 +284,21 @@ GEM
       base64
       websocket-extensions (>= 0.1.0)
     websocket-extensions (0.1.5)
-    zeitwerk (2.7.3)
+    zeitwerk (2.7.4)
 
 PLATFORMS
   ruby
 
 DEPENDENCIES
   devise!
+  minitest (< 6)
   mocha (~> 2.1)
   mongoid (~> 9.0)!
   omniauth
   omniauth-facebook
   omniauth-oauth2
   omniauth-openid
+  ostruct
   rails (~> 8.1.0)
   rails-controller-testing
   rdoc
@@ -305,4 +309,4 @@ DEPENDENCIES
   webrat
 
 BUNDLED WITH
-   2.6.9
+   4.0.3
diff --git a/gemfiles/Gemfile-rails-7-0 b/gemfiles/Gemfile-rails-7-0
index 625664d0..a397d04f 100644
--- a/gemfiles/Gemfile-rails-7-0
+++ b/gemfiles/Gemfile-rails-7-0
@@ -18,6 +18,8 @@ group :test do
   gem "timecop"
   gem "webrat", "0.7.3", require: false
   gem "mocha", "~> 2.1", require: false
+  gem "minitest", "< 6"
+  gem "ostruct"
 end
 
 platforms :ruby do
diff --git a/gemfiles/Gemfile-rails-7-1 b/gemfiles/Gemfile-rails-7-1
index 1eda668a..41caefa8 100644
--- a/gemfiles/Gemfile-rails-7-1
+++ b/gemfiles/Gemfile-rails-7-1
@@ -18,6 +18,8 @@ group :test do
   gem "timecop"
   gem "webrat"
   gem "mocha", "~> 2.1", require: false
+  gem "minitest", "< 6"
+  gem "ostruct"
 end
 
 platforms :ruby do
diff --git a/gemfiles/Gemfile-rails-7-2 b/gemfiles/Gemfile-rails-7-2
index ed06ba5e..2fa2804d 100644
--- a/gemfiles/Gemfile-rails-7-2
+++ b/gemfiles/Gemfile-rails-7-2
@@ -19,6 +19,8 @@ group :test do
   gem "timecop"
   gem "webrat", require: false
   gem "mocha", "~> 2.1", require: false
+  gem "minitest", "< 6"
+  gem "ostruct"
 end
 
 platforms :ruby do
diff --git a/gemfiles/Gemfile-rails-8-0 b/gemfiles/Gemfile-rails-8-0
index 8753badd..23954ff5 100644
--- a/gemfiles/Gemfile-rails-8-0
+++ b/gemfiles/Gemfile-rails-8-0
@@ -18,6 +18,8 @@ group :test do
   gem "timecop"
   gem 'webrat'
   gem "mocha", "~> 2.1", require: false
+  gem "minitest", "< 6"
+  gem "ostruct"
 end
 
 platforms :ruby do
diff --git a/gemfiles/Gemfile-rails-main b/gemfiles/Gemfile-rails-main
index 69d384ac..57ed95a1 100644
--- a/gemfiles/Gemfile-rails-main
+++ b/gemfiles/Gemfile-rails-main
@@ -18,6 +18,8 @@ group :test do
   gem "timecop"
   gem "webrat", "0.7.3", require: false
   gem "mocha", "~> 2.1", require: false
+  gem "minitest", "< 6"
+  gem "ostruct"
 end
 
 platforms :ruby do