diff --git a/activerecord/lib/active_record/relation/delegation.rb b/activerecord/lib/active_record/relation/delegation.rb
index f7c3b3783f..7a53a9d1c7 100644
--- a/activerecord/lib/active_record/relation/delegation.rb
+++ b/activerecord/lib/active_record/relation/delegation.rb
@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "mutex_m"
+
 module ActiveRecord
   module Delegation # :nodoc:
     module DelegateCache # :nodoc:
@@ -31,6 +33,10 @@ module ActiveRecord
         super
       end
 
+      def generate_relation_method(method)
+        generated_relation_methods.generate_method(method)
+      end
+
       protected
         def include_relation_methods(delegate)
           superclass.include_relation_methods(delegate) unless base_class?
@@ -39,27 +45,32 @@ module ActiveRecord
 
       private
         def generated_relation_methods
-          @generated_relation_methods ||= Module.new.tap do |mod|
-            mod_name = "GeneratedRelationMethods"
-            const_set mod_name, mod
-            private_constant mod_name
-          end
+          @generated_relation_methods ||= GeneratedRelationMethods.new
         end
+    end
+
+    class GeneratedRelationMethods < Module # :nodoc:
+      include Mutex_m
+
+      def generate_method(method)
+        synchronize do
+          return if method_defined?(method)
 
-        def generate_relation_method(method)
           if /\A[a-zA-Z_]\w*[!?]?\z/.match?(method)
-            generated_relation_methods.module_eval <<-RUBY, __FILE__, __LINE__ + 1
+            module_eval <<-RUBY, __FILE__, __LINE__ + 1
               def #{method}(*args, &block)
                 scoping { klass.#{method}(*args, &block) }
               end
             RUBY
           else
-            generated_relation_methods.define_method(method) do |*args, &block|
+            define_method(method) do |*args, &block|
               scoping { klass.public_send(method, *args, &block) }
             end
           end
         end
+      end
     end
+    private_constant :GeneratedRelationMethods
 
     extend ActiveSupport::Concern
 
@@ -78,39 +89,17 @@ module ActiveRecord
     module ClassSpecificRelation # :nodoc:
       extend ActiveSupport::Concern
 
-      included do
-        @delegation_mutex = Mutex.new
-      end
-
       module ClassMethods # :nodoc:
         def name
           superclass.name
         end
-
-        def delegate_to_scoped_klass(method)
-          @delegation_mutex.synchronize do
-            return if method_defined?(method)
-
-            if /\A[a-zA-Z_]\w*[!?]?\z/.match?(method)
-              module_eval <<-RUBY, __FILE__, __LINE__ + 1
-                def #{method}(*args, &block)
-                  scoping { @klass.#{method}(*args, &block) }
-                end
-              RUBY
-            else
-              define_method method do |*args, &block|
-                scoping { @klass.public_send(method, *args, &block) }
-              end
-            end
-          end
-        end
       end
 
       private
 
         def method_missing(method, *args, &block)
           if @klass.respond_to?(method)
-            self.class.delegate_to_scoped_klass(method)
+            @klass.generate_relation_method(method)
             scoping { @klass.public_send(method, *args, &block) }
           else
             super