diff --git a/lib/devise/hooks/activatable.rb b/lib/devise/hooks/activatable.rb
index b2eaea199f..f8b14c0ff9 100644
--- a/lib/devise/hooks/activatable.rb
+++ b/lib/devise/hooks/activatable.rb
@@ -7,6 +7,6 @@
   if record && record.respond_to?(:active_for_authentication?) && !record.active_for_authentication?
     scope = options[:scope]
     warden.logout(scope)
-    throw :warden, scope: scope, message: record.inactive_message
+    throw :warden, scope: scope, message: record.inactive_message, locale: options[:locale]
   end
 end
diff --git a/lib/devise/hooks/timeoutable.rb b/lib/devise/hooks/timeoutable.rb
index 772eb142b7..655bcaa6b4 100644
--- a/lib/devise/hooks/timeoutable.rb
+++ b/lib/devise/hooks/timeoutable.rb
@@ -25,7 +25,7 @@
         record.timedout?(last_request_at) &&
         !proxy.remember_me_is_active?(record)
       Devise.sign_out_all_scopes ? proxy.sign_out : proxy.sign_out(scope)
-      throw :warden, scope: scope, message: :timeout
+      throw :warden, scope: scope, message: :timeout, locale: options[:locale]
     end
 
     unless env['devise.skip_trackable']
diff --git a/test/helpers/devise_helper_test.rb b/test/helpers/devise_helper_test.rb
index 754e82d819..8e151c6004 100644
--- a/test/helpers/devise_helper_test.rb
+++ b/test/helpers/devise_helper_test.rb
@@ -14,7 +14,7 @@ class DeviseHelperTest < Devise::IntegrationTest
       mongoid: model_labels
     }
 
-    I18n.available_locales
+    I18n.backend.eager_load!
     I18n.backend.store_translations(:en, translations)
   end
 
diff --git a/test/integration/activatable_test.rb b/test/integration/activatable_test.rb
new file mode 100644
index 0000000000..49c3a61b52
--- /dev/null
+++ b/test/integration/activatable_test.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class ActivatableTest < Devise::IntegrationTest
+  test 'shows the localized error message for inactive accounts' do
+    store_translations(
+      en: { devise: { failure: { unconfirmed: 'Unconfirmed account.' } } },
+      de: { devise: { failure: { unconfirmed: 'Unbestätigtes Konto!' } } }
+    ) do
+      I18n.with_locale(:de) do
+        user = create_user(confirm: false, confirmation_sent_at: 1.hour.ago)
+        get new_user_session_path
+        fill_in 'email', with: user.email
+        fill_in 'password', with: user.password
+        click_button 'Log In'
+
+        assert_contain('Unbestätigtes Konto!')
+      end
+    end
+  end
+end
diff --git a/test/integration/authenticatable_test.rb b/test/integration/authenticatable_test.rb
index ea338f6fc1..045cd61715 100644
--- a/test/integration/authenticatable_test.rb
+++ b/test/integration/authenticatable_test.rb
@@ -334,7 +334,9 @@ class AuthenticationRedirectTest < Devise::IntegrationTest
   end
 
   test 'require_no_authentication should set the already_authenticated flash message as admin' do
-    store_translations :en, devise: { failure: { admin: { already_authenticated: 'You are already signed in as admin.' } } } do
+    store_translations en: {
+      devise: { failure: { admin: { already_authenticated: 'You are already signed in as admin.' } } }
+    } do
       sign_in_as_admin
       visit new_admin_session_path
       assert_equal "You are already signed in as admin.", flash[:alert]
diff --git a/test/integration/confirmable_test.rb b/test/integration/confirmable_test.rb
index c951eb0bbd..7a2b6b1aec 100644
--- a/test/integration/confirmable_test.rb
+++ b/test/integration/confirmable_test.rb
@@ -206,8 +206,8 @@ def resend_confirmation
   end
 
   test 'error message is configurable by resource name' do
-    store_translations :en, devise: {
-      failure: { user: { unconfirmed: "Not confirmed user" } }
+    store_translations en: {
+      devise: { failure: { user: { unconfirmed: "Not confirmed user" } } }
     } do
       sign_in_as_user(confirm: false)
       assert_contain 'Not confirmed user'
diff --git a/test/integration/database_authenticatable_test.rb b/test/integration/database_authenticatable_test.rb
index 20097a8718..cd950fb447 100644
--- a/test/integration/database_authenticatable_test.rb
+++ b/test/integration/database_authenticatable_test.rb
@@ -55,7 +55,9 @@ class DatabaseAuthenticationTest < Devise::IntegrationTest
   end
 
   test 'sign in with invalid email should return to sign in form with error message' do
-    store_translations :en, devise: { failure: { admin: { not_found_in_database: 'Invalid email address' } } } do
+    store_translations en: {
+      devise: { failure: { admin: { not_found_in_database: 'Invalid email address' } } }
+    } do
       sign_in_as_admin do
         fill_in 'email', with: 'wrongemail@test.com'
       end
@@ -76,7 +78,9 @@ class DatabaseAuthenticationTest < Devise::IntegrationTest
 
   test 'when in paranoid mode and without a valid e-mail' do
     swap Devise, paranoid: true do
-      store_translations :en, devise: { failure: { not_found_in_database: 'Not found in database' } } do
+      store_translations en: {
+        devise: { failure: { not_found_in_database: 'Not found in database' } }
+      } do
         sign_in_as_user do
           fill_in 'email', with: 'wrongemail@test.com'
         end
@@ -88,7 +92,9 @@ class DatabaseAuthenticationTest < Devise::IntegrationTest
   end
 
   test 'error message is configurable by resource name' do
-    store_translations :en, devise: { failure: { admin: { invalid: "Invalid credentials" } } } do
+    store_translations en: {
+      devise: { failure: { admin: { invalid: "Invalid credentials" } } }
+    } do
       sign_in_as_admin do
         fill_in 'password', with: 'abcdef'
       end
diff --git a/test/integration/lockable_test.rb b/test/integration/lockable_test.rb
index e5dd5ee08b..78ffc6084d 100644
--- a/test/integration/lockable_test.rb
+++ b/test/integration/lockable_test.rb
@@ -103,10 +103,7 @@ def send_unlock_request
   end
 
   test 'error message is configurable by resource name' do
-    store_translations :en, devise: {
-        failure: {user: {locked: "You are locked!"}}
-    } do
-
+    store_translations en: { devise: { failure: { user: { locked: "You are locked!"} } } } do
       user = create_user(locked: true)
       user.failed_attempts = User.maximum_attempts + 1
       user.save!
@@ -117,10 +114,7 @@ def send_unlock_request
   end
 
   test "user should not be able to sign in when locked" do
-    store_translations :en, devise: {
-        failure: {user: {locked: "You are locked!"}}
-    } do
-
+    store_translations en: { devise: { failure: { user: { locked: "You are locked!"} } } } do
       user = create_user(locked: true)
       user.failed_attempts = User.maximum_attempts + 1
       user.save!
diff --git a/test/integration/timeoutable_test.rb b/test/integration/timeoutable_test.rb
index d11d59105c..f516244b67 100644
--- a/test/integration/timeoutable_test.rb
+++ b/test/integration/timeoutable_test.rb
@@ -141,9 +141,7 @@ def last_request_at
   end
 
   test 'error message with i18n' do
-    store_translations :en, devise: {
-      failure: { user: { timeout: 'Session expired!' } }
-    } do
+    store_translations en: { devise: { failure: { user: { timeout: 'Session expired!' } } } } do
       user = sign_in_as_user
 
       get expire_user_path(user)
@@ -154,9 +152,7 @@ def last_request_at
   end
 
   test 'error message with i18n with double redirect' do
-    store_translations :en, devise: {
-      failure: { user: { timeout: 'Session expired!' } }
-    } do
+    store_translations en: { devise: { failure: { user: { timeout: 'Session expired!' } } } } do
       user = sign_in_as_user
 
       get expire_user_path(user)
@@ -167,6 +163,24 @@ def last_request_at
     end
   end
 
+  test 'shows the localized error message on session timeout' do
+    # Set up the error message in the default and in a different locale
+    store_translations(
+      en: { devise: { failure: { user: { timeout: 'Session expired!' } } } },
+      de: { devise: { failure: { timeout: 'Sitzung abgelaufen!' } } }
+    ) do
+      I18n.with_locale(:de) do
+        user = sign_in_as_user
+
+        get expire_user_path(user)
+        get users_path
+        follow_redirect!
+        follow_redirect!
+        assert_contain('Sitzung abgelaufen!')
+      end
+    end
+  end
+
   test 'time out not triggered if remembered' do
     user = sign_in_as_user remember_me: true
     get expire_user_path(user)
diff --git a/test/mailers/confirmation_instructions_test.rb b/test/mailers/confirmation_instructions_test.rb
index 5b46331219..e339736a54 100644
--- a/test/mailers/confirmation_instructions_test.rb
+++ b/test/mailers/confirmation_instructions_test.rb
@@ -69,13 +69,17 @@ def mail
   end
 
   test 'set up subject from I18n' do
-    store_translations :en, devise: { mailer: { confirmation_instructions: { subject: 'Account Confirmation' } } } do
+    store_translations en: {
+      devise: { mailer: { confirmation_instructions: { subject: 'Account Confirmation' } } }
+    } do
       assert_equal 'Account Confirmation', mail.subject
     end
   end
 
   test 'subject namespaced by model' do
-    store_translations :en, devise: { mailer: { confirmation_instructions: { user_subject: 'User Account Confirmation' } } } do
+    store_translations en: {
+      devise: { mailer: { confirmation_instructions: { user_subject: 'User Account Confirmation' } } }
+    } do
       assert_equal 'User Account Confirmation', mail.subject
     end
   end
diff --git a/test/mailers/email_changed_test.rb b/test/mailers/email_changed_test.rb
index f324165452..8cf26b3759 100644
--- a/test/mailers/email_changed_test.rb
+++ b/test/mailers/email_changed_test.rb
@@ -73,13 +73,17 @@ def mail
   end
 
   test 'set up subject from I18n' do
-    store_translations :en, devise: { mailer: { email_changed: { subject: 'Email Has Changed' } } } do
+    store_translations en: {
+      devise: { mailer: { email_changed: { subject: 'Email Has Changed' } } }
+    } do
       assert_equal 'Email Has Changed', mail.subject
     end
   end
 
   test 'subject namespaced by model' do
-    store_translations :en, devise: { mailer: { email_changed: { user_subject: 'User Email Has Changed' } } } do
+    store_translations en: {
+      devise: { mailer: { email_changed: { user_subject: 'User Email Has Changed' } } }
+    } do
       assert_equal 'User Email Has Changed', mail.subject
     end
   end
diff --git a/test/mailers/reset_password_instructions_test.rb b/test/mailers/reset_password_instructions_test.rb
index 5a344cbf09..164fb7d79e 100644
--- a/test/mailers/reset_password_instructions_test.rb
+++ b/test/mailers/reset_password_instructions_test.rb
@@ -65,13 +65,17 @@ def mail
   end
 
   test 'set up subject from I18n' do
-    store_translations :en, devise: { mailer: { reset_password_instructions: { subject: 'Reset instructions' } } } do
+    store_translations en: {
+      devise: { mailer: { reset_password_instructions: { subject: 'Reset instructions' } } }
+    } do
       assert_equal 'Reset instructions', mail.subject
     end
   end
 
   test 'subject namespaced by model' do
-    store_translations :en, devise: { mailer: { reset_password_instructions: { user_subject: 'User Reset Instructions' } } } do
+    store_translations en: {
+      devise: { mailer: { reset_password_instructions: { user_subject: 'User Reset Instructions' } } }
+    } do
       assert_equal 'User Reset Instructions', mail.subject
     end
   end
diff --git a/test/mailers/unlock_instructions_test.rb b/test/mailers/unlock_instructions_test.rb
index dff580e2eb..e7cc0031d8 100644
--- a/test/mailers/unlock_instructions_test.rb
+++ b/test/mailers/unlock_instructions_test.rb
@@ -66,13 +66,17 @@ def mail
   end
 
   test 'set up subject from I18n' do
-    store_translations :en, devise: { mailer: { unlock_instructions:  { subject: 'Yo unlock instructions' } } } do
+    store_translations en: {
+      devise: { mailer: { unlock_instructions:  { subject: 'Yo unlock instructions' } } }
+    } do
       assert_equal 'Yo unlock instructions', mail.subject
     end
   end
 
   test 'subject namespaced by model' do
-    store_translations :en, devise: { mailer: { unlock_instructions: { user_subject: 'User Unlock Instructions' } } } do
+    store_translations en: {
+      devise: { mailer: { unlock_instructions: { user_subject: 'User Unlock Instructions' } } }
+    } do
       assert_equal 'User Unlock Instructions', mail.subject
     end
   end
diff --git a/test/support/helpers.rb b/test/support/helpers.rb
index 01dc6aa562..3b237c5d07 100644
--- a/test/support/helpers.rb
+++ b/test/support/helpers.rb
@@ -7,13 +7,12 @@ def setup_mailer
     ActionMailer::Base.deliveries = []
   end
 
-  def store_translations(locale, translations, &block)
-    # Calling 'available_locales' before storing the translations to ensure
-    # that the I18n backend will be initialized before we store our custom
-    # translations, so they will always override the translations for the
-    # YML file.
-    I18n.available_locales
-    I18n.backend.store_translations(locale, translations)
+  def store_translations(translations)
+    # Eager-loading the backend before storing the translations ensures that the I18n backend will
+    # always be initialized before we store our custom translations, so the test-specific
+    # translations override the translations from the YML files.
+    I18n.backend.eager_load!
+    translations.each { |locale, entries| I18n.backend.store_translations(locale, entries) }
     yield
   ensure
     I18n.reload!
diff --git a/test/test_helper.rb b/test/test_helper.rb
index e6df812037..8cde508472 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -11,6 +11,8 @@
 require "orm/#{DEVISE_ORM}"
 
 I18n.load_path.concat Dir["#{File.dirname(__FILE__)}/support/locale/*.yml"]
+# Allow setting test-specific locales even if they are not defined in the locale YAML files.
+I18n.enforce_available_locales = false
 
 require 'mocha/minitest'
 require 'timecop'