2 files changed, 36 insertions, 3 deletions
diff --git a/activemodel/lib/active_model/observer_array.rb b/activemodel/lib/active_model/observer_array.rb
index b8aa9cc1e2..f3b5811b81 100644
--- a/activemodel/lib/active_model/observer_array.rb
+++ b/activemodel/lib/active_model/observer_array.rb
@@ -48,7 +48,7 @@ module ActiveModel
       set_enablement(true, observers, &block)
     end
 
-    private
+    protected
 
       def observer_class_for(observer)
         return observer if observer.is_a?(Class)
@@ -61,13 +61,37 @@ module ActiveModel
         end
       end
 
+      def start_transaction
+        disabled_observer_stack.push(disabled_observers.dup)
+        each_subclass_array do |array|
+          array.start_transaction
+        end
+      end
+
+      def disabled_observer_stack
+        @disabled_observer_stack ||= []
+      end
+
+      def end_transaction
+        @disabled_observers = disabled_observer_stack.pop
+        each_subclass_array do |array|
+          array.end_transaction
+        end
+      end
+
       def transaction
-        orig_disabled_observers = disabled_observers.dup
+        start_transaction
 
         begin
           yield
         ensure
-          @disabled_observers = orig_disabled_observers
+          end_transaction
+        end
+      end
+
+      def each_subclass_array
+        model_class.subclasses.each do |subclass|
+          yield self.class.for(subclass)
         end
       end
 
@@ -92,6 +116,10 @@ module ActiveModel
               disabled_observers << klass
             end
           end
+
+          each_subclass_array do |array|
+            array.set_enablement(enabled, observers)
+          end
         end
       end
   end
diff --git a/activemodel/lib/active_model/observing.rb b/activemodel/lib/active_model/observing.rb
index e1a2ce218d..ba6be46670 100644
--- a/activemodel/lib/active_model/observing.rb
+++ b/activemodel/lib/active_model/observing.rb
@@ -70,6 +70,10 @@ module ActiveModel
         observer_instances.size
       end
 
+      def subclasses
+        @subclasses ||= []
+      end
+
       protected
         def instantiate_observer(observer) #:nodoc:
           # string/symbol
@@ -89,6 +93,7 @@ module ActiveModel
         # Notify observers when the observed class is subclassed.
         def inherited(subclass)
           super
+          subclasses << subclass
           notify_observers :observed_class_inherited, subclass
         end
     end