diff --git a/lib/mongo/collection.rb b/lib/mongo/collection.rb
index d98c145..2e1de47 100644
--- a/lib/mongo/collection.rb
+++ b/lib/mongo/collection.rb
@@ -480,7 +480,6 @@ module Mongo
     #
     # @core mapreduce map_reduce-instance_method
     def map_reduce(map, reduce, opts={})
-      opts.assert_valid_keys(:query, :sort, :limit, :finalize, :out, :keeptemp, :verbose, :raw)
       map    = BSON::Code.new(map) unless map.is_a?(BSON::Code)
       reduce = BSON::Code.new(reduce) unless reduce.is_a?(BSON::Code)
       raw    = opts.delete(:raw)
diff --git a/test/collection_test.rb b/test/collection_test.rb
index 269eafa..beae5b9 100644
--- a/test/collection_test.rb
+++ b/test/collection_test.rb
@@ -453,14 +453,6 @@ class TestCollection < Test::Unit::TestCase
       assert res["counts"]
       assert res["timeMillis"]
     end
-
-    def test_allows_only_valid_keys
-      m = Code.new("function() { emit(this.user_id, 1); }")
-      r = Code.new("function(k,vals) { return 1; }")
-      assert_raise ArgumentError do
-        @@test.map_reduce(m, r, :foo => true)
-      end
-    end
   end
 
   if @@version > "1.3.0"