diff --git a/types/backbone/index.d.ts b/types/backbone/index.d.ts
index 607f6413fc..1a186d9924 100644
--- a/types/backbone/index.d.ts
+++ b/types/backbone/index.d.ts
@@ -460,8 +460,7 @@ declare namespace Backbone {
     }
 
     // SYNC
-    function sync(method: string, model: Model, options?: JQueryAjaxSettings): any;
-    function sync(method: string, collection: Collection<Model>, options?: JQueryAjaxSettings): any;
+    function sync(method: string, model: Model | Collection<Model>, options?: JQueryAjaxSettings): any;
     function ajax(options?: JQueryAjaxSettings): JQueryXHR;
     var emulateHTTP: boolean;
     var emulateJSON: boolean;