3 files changed, 10 insertions, 8 deletions
diff --git a/activemodel/lib/active_model/locale/en.yml b/activemodel/lib/active_model/locale/en.yml
index ba49c6beaa..d17848c861 100644
--- a/activemodel/lib/active_model/locale/en.yml
+++ b/activemodel/lib/active_model/locale/en.yml
@@ -9,7 +9,7 @@ en:
       inclusion: "is not included in the list"
       exclusion: "is reserved"
       invalid: "is invalid"
-      confirmation: "doesn't match confirmation"
+      confirmation: "doesn't match %{attribute}"
       accepted: "must be accepted"
       empty: "can't be empty"
       blank: "can't be blank"
diff --git a/activemodel/lib/active_model/observing.rb b/activemodel/lib/active_model/observing.rb
index 99b32300ca..4c7dae42f0 100644
--- a/activemodel/lib/active_model/observing.rb
+++ b/activemodel/lib/active_model/observing.rb
@@ -90,14 +90,15 @@ module ActiveModel
         def instantiate_observer(observer) #:nodoc:
           # string/symbol
           if observer.respond_to?(:to_sym)
-            observer.to_s.camelize.constantize.instance
-          elsif observer.respond_to?(:instance)
+            observer = observer.to_s.camelize.constantize
+          end
+          if observer.respond_to?(:instance)
             observer.instance
           else
             raise ArgumentError,
-              "#{observer} must be a lowercase, underscored class name (or an " +
-              "instance of the class itself) responding to the instance " +
-              "method. Example: Person.observers = :big_brother # calls " +
+              "#{observer} must be a lowercase, underscored class name (or " +
+              "the class itself) responding to the method :instance. " +
+              "Example: Person.observers = :big_brother # calls " +
               "BigBrother.instance"
           end
         end
@@ -202,7 +203,7 @@ module ActiveModel
       def observe(*models)
         models.flatten!
         models.collect! { |model| model.respond_to?(:to_sym) ? model.to_s.camelize.constantize : model }
-        redefine_method(:observed_classes) { models }
+        singleton_class.redefine_method(:observed_classes) { models }
       end
 
       # Returns an array of Classes to observe.
diff --git a/activemodel/lib/active_model/validations/confirmation.rb b/activemodel/lib/active_model/validations/confirmation.rb
index e8526303e2..69ab74734d 100644
--- a/activemodel/lib/active_model/validations/confirmation.rb
+++ b/activemodel/lib/active_model/validations/confirmation.rb
@@ -5,7 +5,8 @@ module ActiveModel
     class ConfirmationValidator < EachValidator
       def validate_each(record, attribute, value)
         if (confirmed = record.send("#{attribute}_confirmation")) && (value != confirmed)
-          record.errors.add(attribute, :confirmation, options)
+          human_attribute_name = record.class.human_attribute_name(attribute)
+          record.errors.add(:"#{attribute}_confirmation", :confirmation, options.merge(:attribute => human_attribute_name))
         end
       end