diff --git a/types/backbone/backbone-tests.ts b/types/backbone/backbone-tests.ts
index c074ac57e5..967ae5d52d 100644
--- a/types/backbone/backbone-tests.ts
+++ b/types/backbone/backbone-tests.ts
@@ -178,6 +178,8 @@ function test_collection() {
 
     var alphabetical = books.sortBy((book: Book): number => null);
 
+    var copy = books.clone();
+
     let one: Book;
     let models: Book[];
     let bool: boolean;