diff --git a/mongoose/mongoose-tests.ts b/mongoose/mongoose-tests.ts
index de68f006a..4ccc9b72d 100644
--- a/mongoose/mongoose-tests.ts
+++ b/mongoose/mongoose-tests.ts
@@ -368,6 +368,7 @@ schema.virtual('display_name')
   .set((value: string): void => {});
 
 var id: mongoose.Types.ObjectId = new mongoose.Types.ObjectId('foo');
+var id: mongoose.Types.ObjectId = new mongoose.Types.ObjectId();
 var id2: mongoose.Types.ObjectId = new mongoose.Types.ObjectId(123);
 var id2: mongoose.Types.ObjectId = mongoose.Types.ObjectId.createFromTime(123);
 var id2: mongoose.Types.ObjectId = mongoose.Types.ObjectId.createFromHexString('foo');
@@ -377,4 +378,4 @@ var eq = id.equals(id2);
 
 var kitty1 = new Kitty({});
 var kitty2 = new Kitty({});
-var kittyEq = kitty1._id.equals(kitty2._id);
\ No newline at end of file
+var kittyEq = kitty1._id.equals(kitty2._id);
diff --git a/mongoose/mongoose.d.ts b/mongoose/mongoose.d.ts
index 29e167dcd..64bfd3d01 100644
--- a/mongoose/mongoose.d.ts
+++ b/mongoose/mongoose.d.ts
@@ -79,7 +79,7 @@ declare module "mongoose" {
   }
   export module Types {
     export class ObjectId {
-      constructor(id: string|number);
+      constructor(id?: string|number);
       toHexString(): string;
       equals(other: ObjectId): boolean;
       getTimestamp(): Date;
@@ -458,4 +458,3 @@ declare module "mongoose" {
   }
 
 }
-