1 files changed, 14 insertions, 4 deletions
diff --git a/activerecord/lib/active_record/attribute_methods/dirty.rb b/activerecord/lib/active_record/attribute_methods/dirty.rb
index b0e1391cb9..6aa414ba6b 100644
--- a/activerecord/lib/active_record/attribute_methods/dirty.rb
+++ b/activerecord/lib/active_record/attribute_methods/dirty.rb
@@ -50,7 +50,7 @@ module ActiveRecord
         super.tap do
           @previous_mutation_tracker = nil
           clear_mutation_trackers
-          @changed_attributes = HashWithIndifferentAccess.new
+          @changed_attributes = ActiveSupport::HashWithIndifferentAccess.new
         end
       end
 
@@ -70,13 +70,13 @@ module ActiveRecord
 
       def changes_applied
         @previous_mutation_tracker = mutation_tracker
-        @changed_attributes = HashWithIndifferentAccess.new
+        @changed_attributes = ActiveSupport::HashWithIndifferentAccess.new
         clear_mutation_trackers
       end
 
       def clear_changes_information
         @previous_mutation_tracker = nil
-        @changed_attributes = HashWithIndifferentAccess.new
+        @changed_attributes = ActiveSupport::HashWithIndifferentAccess.new
         forget_attribute_assignments
         clear_mutation_trackers
       end
@@ -275,7 +275,17 @@ module ActiveRecord
 
         def attribute_will_change!(attr_name)
           super
-          mutations_from_database.force_change(attr_name)
+          if self.class.has_attribute?(attr_name)
+            mutations_from_database.force_change(attr_name)
+          else
+            ActiveSupport::Deprecation.warn(<<-EOW.squish)
+              #{attr_name} is not an attribute known to Active Record.
+              This behavior is deprecated and will be removed in the next
+              version of Rails. If you'd like #{attr_name} to be managed
+              by Active Record, add `attribute :#{attr_name} to your class.
+            EOW
+            mutations_from_database.deprecated_force_change(attr_name)
+          end
         end
 
         def _update_record(*)