diff --git a/lib/mongo/cursor.rb b/lib/mongo/cursor.rb
index 75cb69c..967d868 100644
--- a/lib/mongo/cursor.rb
+++ b/lib/mongo/cursor.rb
@@ -299,10 +299,10 @@ module Mongo
          selector
         when nil
           {}
-        when String
-          {"$where" => Code.new(selector)}
-        when Code
+        when BSON::Code
           {"$where" => selector}
+        when String
+          {"$where" => BSON::Code.new(selector)}
       end
     end
 
diff --git a/test/db_api_test.rb b/test/db_api_test.rb
index 5a5113b..9bc88f5 100644
--- a/test/db_api_test.rb
+++ b/test/db_api_test.rb
@@ -469,8 +469,18 @@ class DBAPITest < Test::Unit::TestCase
     @@coll.insert('a' => 3)
 
     assert_equal 3, @@coll.count
-    assert_equal 1, @@coll.find('$where' => Code.new('this.a > 2')).count()
-    assert_equal 2, @@coll.find('$where' => Code.new('this.a > i', {'i' => 1})).count()
+    assert_equal 1, @@coll.find('$where' => BSON::Code.new('this.a > 2')).count()
+    assert_equal 2, @@coll.find('$where' => BSON::Code.new('this.a > i', {'i' => 1})).count()
+  end
+
+  def test_implicit_where
+    @@coll.remove
+    @@coll.insert('a' => 2)
+    @@coll.insert('a' => 3)
+
+    assert_equal 2, @@coll.count
+    assert_equal 1, @@coll.find('this.a > 2').count()
+    assert_equal 2, @@coll.find(BSON::Code.new('this.a > z', {'z' => 1})).to_a.length
   end
 
   def test_eval
diff --git a/test/mongo_bson/bson_test.rb b/test/mongo_bson/bson_test.rb
index 0290802..53f664a 100644
--- a/test/mongo_bson/bson_test.rb
+++ b/test/mongo_bson/bson_test.rb
@@ -98,6 +98,12 @@ class BSONTest < Test::Unit::TestCase
     assert_equal doc, BSON::BSON_CODER.deserialize(bson)
   end
 
+  def test_code_with_scope
+    doc = {'$where' => Code.new('this.a.b < this.b', {'foo' => 1})}
+    bson = BSON::BSON_CODER.serialize(doc)
+    assert_equal doc, BSON::BSON_CODER.deserialize(bson)
+  end
+
   def test_number
     doc = {'doc' => 41.99}
     bson = BSON::BSON_CODER.serialize(doc)