diff --git a/lib/mongo/cursor.rb b/lib/mongo/cursor.rb
index 0ed33d2..42d84fd 100644
--- a/lib/mongo/cursor.rb
+++ b/lib/mongo/cursor.rb
@@ -34,6 +34,8 @@ module Mongo
     #
     # @core cursors constructor_details
     def initialize(collection, opts={})
+      @cursor_id  = nil
+
       @db         = collection.db
       @collection = collection
       @connection = @db.connection