diff --git a/src/core.js b/src/core.js
index cab3b54c..ee4ac705 100644
--- a/src/core.js
+++ b/src/core.js
@@ -12,6 +12,9 @@ var jQuery = function( selector, context ) {
 	// Map over the $ in case of overwrite
 	_$ = window.$,
 
+	// Use the correct document accordingly with window argument (sandbox)
+	document = window.document,
+
 	// A central reference to the root jQuery(document)
 	rootjQuery,