diff --git a/activerecord/test/lifecycle_test.rb b/activerecord/test/lifecycle_test.rb
index b411524cffd87e199a5283ede3486b25cac8f53d..2fdeb4181e023c05da0c2c11d651f9bb52bd4310 100755
--- a/activerecord/test/lifecycle_test.rb
+++ b/activerecord/test/lifecycle_test.rb
@@ -75,6 +75,7 @@ def test_before_destroy
 
   def test_after_save
     ActiveRecord::Base.observers = :topic_manual_observer
+    ActiveRecord::Base.instantiate_observers
 
     topic = Topic.find(1)
     topic.title = "hello"
@@ -86,6 +87,7 @@ def test_after_save
 
   def test_observer_update_on_save
     ActiveRecord::Base.observers = TopicManualObserver
+    ActiveRecord::Base.instantiate_observers
 
     topic = Topic.find(1)
     assert TopicManualObserver.instance.has_been_notified?
@@ -130,6 +132,6 @@ def test_observing_subclasses
   end
 
   def test_invalid_observer
-    assert_raise(ArgumentError) { Topic.observers = Object.new }
+    assert_raise(ArgumentError) { Topic.observers = Object.new; Topic.instantiate_observers }
   end
 end