2 files changed, 21 insertions, 5 deletions
diff --git a/activesupport/lib/active_support/json/encoding.rb b/activesupport/lib/active_support/json/encoding.rb
index 02c233595d..dd94315111 100644
--- a/activesupport/lib/active_support/json/encoding.rb
+++ b/activesupport/lib/active_support/json/encoding.rb
@@ -128,12 +128,21 @@ module ActiveSupport
   end
 end
 
-class Object
-  # Dumps object in JSON (JavaScript Object Notation). See www.json.org for more info.
-  def to_json(options = nil)
-    ActiveSupport::JSON.encode(self, options)
-  end
+# The JSON gem adds a few modules to Ruby core classes containing :to_json definition, overwriting
+# their default behavior. That said, we need to define the basic to_json method in all of them,
+# otherwise they will always use to_json gem implementation, which is backwards incompatible in
+# several cases (for instance, the JSON implementation for Hash does not work) with inheritance
+# and consequently classes as ActiveSupport::OrderedHash cannot be serialized to json.
+[Object, Array, FalseClass, Float, Hash, Integer, NilClass, String, TrueClass].each do |klass|
+  klass.class_eval <<-RUBY, __FILE__, __LINE__
+    # Dumps object in JSON (JavaScript Object Notation). See www.json.org for more info.
+    def to_json(options = nil)
+      ActiveSupport::JSON.encode(self, options)
+    end
+  RUBY
+end
 
+class Object
   def as_json(options = nil) #:nodoc:
     if respond_to?(:to_hash)
       to_hash
diff --git a/activesupport/test/ordered_hash_test.rb b/activesupport/test/ordered_hash_test.rb
index dca5c5d0c0..f3d2ec0286 100644
--- a/activesupport/test/ordered_hash_test.rb
+++ b/activesupport/test/ordered_hash_test.rb
@@ -1,4 +1,5 @@
 require 'abstract_unit'
+require 'active_support/json'
 
 class OrderedHashTest < Test::Unit::TestCase
   def setup
@@ -185,6 +186,12 @@ class OrderedHashTest < Test::Unit::TestCase
     assert @ordered_hash.inspect.include?(@hash.inspect)
   end
 
+  def test_json
+    ordered_hash = ActiveSupport::OrderedHash[:foo, :bar]
+    hash = Hash[:foo, :bar]
+    assert_equal ordered_hash.to_json, hash.to_json
+  end
+
   def test_alternate_initialization_with_splat
     alternate = ActiveSupport::OrderedHash[1,2,3,4]
     assert_kind_of ActiveSupport::OrderedHash, alternate