2 files changed, 33 insertions, 1 deletions
diff --git a/activerecord/lib/active_record/attribute_methods/serialization.rb b/activerecord/lib/active_record/attribute_methods/serialization.rb
index 9caf73e627..1287de0d0d 100644
--- a/activerecord/lib/active_record/attribute_methods/serialization.rb
+++ b/activerecord/lib/active_record/attribute_methods/serialization.rb
@@ -56,7 +56,11 @@ module ActiveRecord
         end
 
         def type_cast(value)
-          value.unserialized_value @column.type_cast value.value
+          if value.state == :serialized
+            value.unserialized_value @column.type_cast value.value
+          else
+            value.unserialized_value
+          end
         end
 
         def type
diff --git a/activerecord/test/cases/attribute_methods/serialization_test.rb b/activerecord/test/cases/attribute_methods/serialization_test.rb
new file mode 100644
index 0000000000..8ce6192096
--- /dev/null
+++ b/activerecord/test/cases/attribute_methods/serialization_test.rb
@@ -0,0 +1,28 @@
+require "cases/helper"
+
+module ActiveRecord
+  module AttributeMethods
+    class SerializationTest < ActiveSupport::TestCase
+      class FakeColumn < Struct.new(:name)
+        def type; :integer; end
+        def type_cast(s); "#{s}!"; end
+      end
+
+      def test_type_cast_serialized_value
+        value = stub(state: :serialized, value: "Hello world")
+        value.expects(:unserialized_value).with("Hello world!")
+
+        type = Serialization::Type.new(FakeColumn.new)
+        type.type_cast(value)
+      end
+
+      def test_type_cast_unserialized_value
+        value = stub(state: :unserialized, value: "Hello world")
+        value.expects(:unserialized_value).with()
+
+        type = Serialization::Type.new(FakeColumn.new)
+        type.type_cast(value)
+      end
+    end
+  end
+end