diff --git a/activerecord/lib/active_record/associations/collection_proxy.rb b/activerecord/lib/active_record/associations/collection_proxy.rb
index 5d6676f0dfac9014500cf6f79b8e733be873a2cc..74a4d515c2f4882a3f0bf85e2263c67b85c1873e 100644
--- a/activerecord/lib/active_record/associations/collection_proxy.rb
+++ b/activerecord/lib/active_record/associations/collection_proxy.rb
@@ -1121,6 +1121,19 @@ def reset
 
       delegate(*delegate_methods, to: :scope)
 
+      module DelegateExtending # :nodoc:
+        private
+          def method_missing(method, *args, &block)
+            extending_values = association_scope.extending_values
+            if extending_values.any? && (extending_values - self.class.included_modules).any?
+              self.class.include(*extending_values)
+              public_send(method, *args, &block)
+            else
+              super
+            end
+          end
+      end
+
       private
 
         def find_nth_with_limit(index, limit)
@@ -1141,21 +1154,16 @@ def find_from_target?
           @association.find_from_target?
         end
 
+        def association_scope
+          @association.association_scope
+        end
+
         def exec_queries
           load_target
         end
 
         def respond_to_missing?(method, _)
-          scope.respond_to?(method) || super
-        end
-
-        def method_missing(method, *args, &block)
-          if scope.respond_to?(method) && scope.extending_values.any?
-            extend(*scope.extending_values)
-            public_send(method, *args, &block)
-          else
-            super
-          end
+          association_scope.respond_to?(method) || super
         end
     end
   end
diff --git a/activerecord/lib/active_record/relation/delegation.rb b/activerecord/lib/active_record/relation/delegation.rb
index 8b4dd256897a9ac006c97218f6b69502e02fdaeb..257ae04ff480a639b3d423ee1be09871998c9aa7 100644
--- a/activerecord/lib/active_record/relation/delegation.rb
+++ b/activerecord/lib/active_record/relation/delegation.rb
@@ -25,6 +25,8 @@ def initialize_relation_delegate_cache
 
       def inherited(child_class)
         child_class.initialize_relation_delegate_cache
+        delegate = child_class.relation_delegate_class(ActiveRecord::Associations::CollectionProxy)
+        delegate.include ActiveRecord::Associations::CollectionProxy::DelegateExtending
         super
       end
     end
diff --git a/activerecord/test/models/comment.rb b/activerecord/test/models/comment.rb
index a4b81d56e0538113cdcdb1920431d3b072d93f4f..76b484e6161ec136a19347543ad384c5a6696827 100644
--- a/activerecord/test/models/comment.rb
+++ b/activerecord/test/models/comment.rb
@@ -19,6 +19,11 @@ class Comment < ActiveRecord::Base
   has_many :children, class_name: "Comment", foreign_key: :parent_id
   belongs_to :parent, class_name: "Comment", counter_cache: :children_count
 
+  # Should not be called if extending modules that having the method exists on an association.
+  def self.greeting
+    raise
+  end
+
   def self.what_are_you
     "a comment..."
   end