diff --git a/lib/devise.rb b/lib/devise.rb
index 3d9dc7886..5b7417ed6 100644
--- a/lib/devise.rb
+++ b/lib/devise.rb
@@ -274,8 +274,14 @@ module Test
   # PRIVATE CONFIGURATION
 
   # Store scopes mappings.
-  mattr_reader :mappings
   @@mappings = {}
+  def self.mappings
+    # Starting from Rails 8.0, routes are lazy-loaded by default in test and development environments.
+    # However, Devise's mappings are built during the routes loading phase.
+    # To ensure it works correctly, we need to load the routes first before accessing @@mappings.
+    Rails.application.try(:reload_routes_unless_loaded)
+    @@mappings
+  end
 
   # OmniAuth configurations.
   mattr_reader :omniauth_configs