diff --git a/actionpack/test/controller/routing_test.rb b/actionpack/test/controller/routing_test.rb
index ce5c899a19..cd067b7d18 100644
--- a/actionpack/test/controller/routing_test.rb
+++ b/actionpack/test/controller/routing_test.rb
@@ -1444,7 +1444,7 @@ def test_escape_spaces_build_query_string
   end
 
   def test_expand_array_build_query_string
-    assert_uri_equal '/foo?x[]=1&x[]=2', default_route_set.generate({:controller => 'foo', :x => [1, 2]})
+    assert_uri_equal '/foo?x%5B%5D=1&x%5B%5D=2', default_route_set.generate({:controller => 'foo', :x => [1, 2]})
   end
 
   def test_escape_spaces_build_query_string_selected_keys
@@ -1744,9 +1744,9 @@ def test_generate
     assert_equal '/posts', @routes.generate({:controller => 'posts'}, {:controller => 'posts', :action => 'index'})
     assert_equal '/posts/create', @routes.generate({:action => 'create'}, {:controller => 'posts'})
     assert_equal '/posts?foo=bar', @routes.generate(:controller => 'posts', :foo => 'bar')
-    assert_equal '/posts?foo[]=bar&foo[]=baz', @routes.generate(:controller => 'posts', :foo => ['bar', 'baz'])
+    assert_equal '/posts?foo%5B%5D=bar&foo%5B%5D=baz', @routes.generate(:controller => 'posts', :foo => ['bar', 'baz'])
     assert_equal '/posts?page=2', @routes.generate(:controller => 'posts', :page => 2)
-    assert_equal '/posts?q[foo][a]=b', @routes.generate(:controller => 'posts', :q => { :foo => { :a => 'b'}})
+    assert_equal '/posts?q%5Bfoo%5D%5Ba%5D=b', @routes.generate(:controller => 'posts', :q => { :foo => { :a => 'b'}})
 
     assert_equal '/news.rss', @routes.generate(:controller => 'news', :action => 'index', :format => 'rss')
 
diff --git a/activesupport/lib/active_support/core_ext/object/to_param.rb b/activesupport/lib/active_support/core_ext/object/to_param.rb
index ecb2bca82c..593f376159 100644
--- a/activesupport/lib/active_support/core_ext/object/to_param.rb
+++ b/activesupport/lib/active_support/core_ext/object/to_param.rb
@@ -1,5 +1,3 @@
-
-
 class Object
   # Alias of <tt>to_s</tt>.
   def to_param
@@ -41,7 +39,7 @@ class Hash
   # ==== Examples
   #   { :name => 'David', :nationality => 'Danish' }.to_param # => "name=David&nationality=Danish"
   #
-  #   { :name => 'David', :nationality => 'Danish' }.to_param('user') # => "user[name]=David&user[nationality]=Danish"
+  #   { :name => 'David', :nationality => 'Danish' }.to_query('user') # => "user%5Bname%5D=David&user%5Bnationality%5D=Danish"
   def to_param(namespace = nil)
     collect do |key, value|
       value.to_query(namespace ? "#{namespace}[#{key}]" : key)
diff --git a/activesupport/lib/active_support/core_ext/object/to_query.rb b/activesupport/lib/active_support/core_ext/object/to_query.rb
index c9981895b4..3f1540f685 100644
--- a/activesupport/lib/active_support/core_ext/object/to_query.rb
+++ b/activesupport/lib/active_support/core_ext/object/to_query.rb
@@ -7,7 +7,7 @@ class Object
   # Note: This method is defined as a default implementation for all Objects for Hash#to_query to work.
   def to_query(key)
     require 'cgi' unless defined?(CGI) && defined?(CGI::escape)
-    "#{CGI.escape(key.to_s).gsub(/%(5B|5D)/n) { [$1].pack('H*') }}=#{CGI.escape(to_param.to_s)}"
+    "#{CGI.escape(key.to_s)}=#{CGI.escape(to_param.to_s)}"
   end
 end
 
@@ -15,7 +15,7 @@ class Array
   # Converts an array into a string suitable for use as a URL query string,
   # using the given +key+ as the param name.
   #
-  #   ['Rails', 'coding'].to_query('hobbies') # => "hobbies[]=Rails&hobbies[]=coding"
+  #   ['Rails', 'coding'].to_query('hobbies') # => "hobbies%5B%5D=Rails&hobbies%5B%5D=coding"
   def to_query(key)
     prefix = "#{key}[]"
     collect { |value| value.to_query(prefix) }.join '&'
diff --git a/activesupport/test/core_ext/object/to_query_test.rb b/activesupport/test/core_ext/object/to_query_test.rb
index e28b4cd493..84da52f4bf 100644
--- a/activesupport/test/core_ext/object/to_query_test.rb
+++ b/activesupport/test/core_ext/object/to_query_test.rb
@@ -18,22 +18,22 @@ def empty.to_param; nil end
   end
 
   def test_nested_conversion
-    assert_query_equal 'person[login]=seckar&person[name]=Nicholas',
+    assert_query_equal 'person%5Blogin%5D=seckar&person%5Bname%5D=Nicholas',
       :person => ActiveSupport::OrderedHash[:login, 'seckar', :name, 'Nicholas']
   end
 
   def test_multiple_nested
-    assert_query_equal 'account[person][id]=20&person[id]=10',
+    assert_query_equal 'account%5Bperson%5D%5Bid%5D=20&person%5Bid%5D=10',
       ActiveSupport::OrderedHash[:account, {:person => {:id => 20}}, :person, {:id => 10}]
   end
 
   def test_array_values
-    assert_query_equal 'person[id][]=10&person[id][]=20',
+    assert_query_equal 'person%5Bid%5D%5B%5D=10&person%5Bid%5D%5B%5D=20',
       :person => {:id => [10, 20]}
   end
 
   def test_array_values_are_not_sorted
-    assert_query_equal 'person[id][]=20&person[id][]=10',
+    assert_query_equal 'person%5Bid%5D%5B%5D=20&person%5Bid%5D%5B%5D=10',
       :person => {:id => [20, 10]}
   end