diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index 34e643b2de19ea2d2414e8ba6c8ee9a04da76aad..38b720ffc8fea491db4d8de6590645a67085234d 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -313,6 +313,13 @@ def scoping
       klass.current_scope = previous
     end
 
+    def _exec_scope(*args, &block) # :nodoc:
+      @delegate_to_klass = true
+      instance_exec(*args, &block) || self
+    ensure
+      @delegate_to_klass = false
+    end
+
     # Updates all records in the current relation with details given. This method constructs a single SQL UPDATE
     # statement and sends it straight to the database. It does not instantiate the involved models and it does not
     # trigger Active Record callbacks or validations. However, values passed to #update_all will still go through
diff --git a/activerecord/lib/active_record/relation/delegation.rb b/activerecord/lib/active_record/relation/delegation.rb
index 4b16b49cdf2b5ce4b83a24c202c88c7daf463d52..27450ab8b372c981bc69918a154bb60e7c4d20bc 100644
--- a/activerecord/lib/active_record/relation/delegation.rb
+++ b/activerecord/lib/active_record/relation/delegation.rb
@@ -82,6 +82,9 @@ def method_missing(method, *args, &block)
           if @klass.respond_to?(method)
             self.class.delegate_to_scoped_klass(method)
             scoping { @klass.public_send(method, *args, &block) }
+          elsif defined?(@delegate_to_klass) &&
+            @delegate_to_klass && @klass.respond_to?(method, true)
+            @klass.send(method, *args, &block)
           elsif arel.respond_to?(method)
             ActiveSupport::Deprecation.warn \
               "Delegating #{method} to arel is deprecated and will be removed in Rails 6.0."
diff --git a/activerecord/lib/active_record/scoping/named.rb b/activerecord/lib/active_record/scoping/named.rb
index 752655aa05f2866c21877048f7dbe9817c7f8eba..a78400158773bfb7e3bcdfe04b10bc226b83c294 100644
--- a/activerecord/lib/active_record/scoping/named.rb
+++ b/activerecord/lib/active_record/scoping/named.rb
@@ -183,7 +183,7 @@ def scope(name, body, &block)
           if body.respond_to?(:to_proc)
             singleton_class.send(:define_method, name) do |*args|
               scope = all
-              scope = scope.instance_exec(*args, &body) || scope
+              scope = scope._exec_scope(*args, &body)
               scope = scope.extending(extension) if extension
               scope
             end
diff --git a/activerecord/test/models/topic.rb b/activerecord/test/models/topic.rb
index 8cd4dc352a4eb0bb74e4467c0ce9d8b4353ba527..a924cf86ae847375ad04260b50c59acfc67cf4e1 100644
--- a/activerecord/test/models/topic.rb
+++ b/activerecord/test/models/topic.rb
@@ -12,9 +12,16 @@ class Topic < ActiveRecord::Base
 
   scope :scope_with_lambda, lambda { all }
 
-  scope :by_lifo, -> { where(author_name: "lifo") }
+  scope :by_lifo, -> { where(author_name: author_name) }
   scope :replied, -> { where "replies_count > 0" }
 
+  class << self
+    private
+      def author_name
+        "lifo"
+      end
+  end
+
   scope "approved_as_string", -> { where(approved: true) }
   scope :anonymous_extension, -> {} do
     def one