diff --git a/activemodel/lib/active_model/observing.rb b/activemodel/lib/active_model/observing.rb
index f3781f7a68..4c7dae42f0 100644
--- a/activemodel/lib/active_model/observing.rb
+++ b/activemodel/lib/active_model/observing.rb
@@ -113,13 +113,21 @@ module ActiveModel
     private
       # Fires notifications to model's observers
       #
-      # def save
-      #   notify_observers(:before_save)
-      #   ...
-      #   notify_observers(:after_save)
-      # end
-      def notify_observers(method)
-        self.class.notify_observers(method, self)
+      #   def save
+      #     notify_observers(:before_save)
+      #     ...
+      #     notify_observers(:after_save)
+      #   end
+      #
+      # Custom notifications can be sent in a similar fashion:
+      #
+      #   notify_observers(:custom_notification, :foo)
+      #
+      # This will call +custom_notification+, passing as arguments
+      # the current object and :foo.
+      #
+      def notify_observers(method, *extra_args)
+        self.class.notify_observers(method, self, *extra_args)
       end
   end
 
@@ -230,10 +238,10 @@ module ActiveModel
 
     # Send observed_method(object) if the method exists and
     # the observer is enabled for the given object's class.
-    def update(observed_method, object, &block) #:nodoc:
+    def update(observed_method, object, *extra_args, &block) #:nodoc:
       return unless respond_to?(observed_method)
       return if disabled_for?(object)
-      send(observed_method, object, &block)
+      send(observed_method, object, *extra_args, &block)
     end
 
     # Special method sent by the observed class when it is inherited.
diff --git a/activemodel/test/cases/observing_test.rb b/activemodel/test/cases/observing_test.rb
index 9891be8d77..c91938a7ee 100644
--- a/activemodel/test/cases/observing_test.rb
+++ b/activemodel/test/cases/observing_test.rb
@@ -14,8 +14,8 @@ class FooObserver < ActiveModel::Observer
 
   attr_accessor :stub
 
-  def on_spec(record)
-    stub.event_with(record) if stub
+  def on_spec(record, *args)
+    stub.event_with(record, *args) if stub
   end
 
   def around_save(record)
@@ -141,6 +141,13 @@ class ObserverTest < ActiveModel::TestCase
     Foo.send(:notify_observers, :on_spec, foo)
   end
 
+  test "passes extra arguments" do
+    foo = Foo.new
+    FooObserver.instance.stub = stub
+    FooObserver.instance.stub.expects(:event_with).with(foo, :bar)
+    Foo.send(:notify_observers, :on_spec, foo, :bar)
+  end
+
   test "skips nonexistent observer event" do
     foo = Foo.new
     Foo.send(:notify_observers, :whatever, foo)