OrderedHash is not necessary with Ruby 1.9, so we stub out the innards of the class but keep the class for code compatability.

lib/mongo/util/ordered_hash.rb

@@ -15,8 +15,14 @@
 # ++
 
 # A hash in which the order of keys are preserved.
+#
+# Under Ruby 1.9 and greater, this class has no added methods because Ruby's
+# Hash already keeps its keys ordered by order of insertion.
 class OrderedHash < Hash
 
+  # We only need the body of this class if the RUBY_VERSION is before 1.9
+  if RUBY_VERSION < '1.9'
+
   attr_accessor :ordered_keys
 
   def keys
@@ -57,4 +63,6 @@ class OrderedHash < Hash
     str << '}'
   end
 
+  end                           # Ruby before 1.9
+
 end