3 files changed, 16 insertions, 4 deletions
diff --git a/activemodel/lib/active_model/errors.rb b/activemodel/lib/active_model/errors.rb
index c6535082d3..5cd8f77f0d 100644
--- a/activemodel/lib/active_model/errors.rb
+++ b/activemodel/lib/active_model/errors.rb
@@ -78,6 +78,11 @@ module ActiveModel
       @messages = ActiveSupport::OrderedHash.new
     end
 
+    def initialize_dup(other)
+      @messages = other.messages.dup
+      super
+    end
+
     # Clear the messages
     def clear
       messages.clear
@@ -118,7 +123,7 @@ module ActiveModel
     #   p.errors[:name] = "must be set"
     #   p.errors[:name] # => ['must be set']
     def []=(attribute, error)
-      self[attribute.to_sym] << error
+      self[attribute] << error
     end
 
     # Iterates through each error key, value pair in the error messages hash.
diff --git a/activemodel/test/cases/errors_test.rb b/activemodel/test/cases/errors_test.rb
index 4edeece3e8..ab80f193b6 100644
--- a/activemodel/test/cases/errors_test.rb
+++ b/activemodel/test/cases/errors_test.rb
@@ -40,6 +40,14 @@ class ErrorsTest < ActiveModel::TestCase
     assert errors.include?(:foo), 'errors should include :foo'
   end
 
+  def test_dup
+    errors = ActiveModel::Errors.new(self)
+    errors[:foo] = 'bar'
+    errors_dup = errors.dup
+    errors_dup[:bar] = 'omg'
+    assert_not_same errors_dup.messages, errors.messages
+  end
+
   def test_has_key?
     errors = ActiveModel::Errors.new(self)
     errors[:foo] = 'omg'
diff --git a/activesupport/lib/active_support/tagged_logging.rb b/activesupport/lib/active_support/tagged_logging.rb
index dc3ca25938..4e2e1a1ff5 100644
--- a/activesupport/lib/active_support/tagged_logging.rb
+++ b/activesupport/lib/active_support/tagged_logging.rb
@@ -14,7 +14,6 @@ module ActiveSupport
   class TaggedLogging
     def initialize(logger)
       @logger = logger
-      @tags   = Hash.new { |h,k| h[k] = [] }
     end
 
     def tagged(*new_tags)
@@ -39,7 +38,7 @@ module ActiveSupport
     end
 
     def flush
-      @tags.delete(Thread.current)
+      current_tags.clear
       @logger.flush if @logger.respond_to?(:flush)
     end
 
@@ -57,7 +56,7 @@ module ActiveSupport
     end
 
     def current_tags
-      @tags[Thread.current]
+      Thread.current[:activesupport_tagged_logging_tags] ||= []
     end
   end
 end