diff --git a/activerecord/CHANGELOG b/activerecord/CHANGELOG
index b14fb50662fd8..dc18983ff63ec 100644
--- a/activerecord/CHANGELOG
+++ b/activerecord/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Change AR::Base#to_param to return a String instead of a Fixnum. Closes #5320. [Nicholas Seckar]
+
 * Use explicit delegation instead of method aliasing for AR::Base.to_param -> AR::Base.id. #5299 (skaes@web.de)
 
 * Refactored ActiveRecord::Base.to_xml to become a delegate for XmlSerializer, which restores sanity to the mega method. This refactoring also reinstates the opinions that type="string" is redundant and ugly and nil-differentiation is not a concern of serialization [DHH]
diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index dee460d9c5242..fe528f514ccd6 100755
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -1410,8 +1410,8 @@ def id
 
       # Enables Active Record objects to be used as URL parameters in Action Pack automatically.
       def to_param
-        # can't use alias_method here, because method 'id' optimizes itself on the fly
-        id
+        # We can't use alias_method here, because method 'id' optimizes itself on the fly.
+        id.to_s if id # Be sure to stringify the id for routes
       end
 
       def id_before_type_cast #:nodoc:
diff --git a/activerecord/test/base_test.rb b/activerecord/test/base_test.rb
index 44b7aea942062..2cbc2cfd2bfa2 100755
--- a/activerecord/test/base_test.rb
+++ b/activerecord/test/base_test.rb
@@ -1316,6 +1316,10 @@ def test_type_name_with_module_should_handle_beginning
     assert_equal 'ActiveRecord::Person', ActiveRecord::Base.send(:type_name_with_module, 'Person')
     assert_equal '::Person', ActiveRecord::Base.send(:type_name_with_module, '::Person')
   end
+  
+  def test_to_param_should_return_string
+    assert_kind_of String, Client.find(:first).to_param
+  end
 
   # FIXME: this test ought to run, but it needs to run sandboxed so that it
   # doesn't b0rk the current test environment by undefing everything.