diff -r 000000000000 -r 6474c204b198 js/src/tests/test262/ch11/11.13/11.13.2/S11.13.2_A4.5_T2.8.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/test262/ch11/11.13/11.13.2/S11.13.2_A4.5_T2.8.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,38 @@
+// Copyright 2009 the Sputnik authors.  All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/**
+ * The production x -= y is the same as x = x - y
+ *
+ * @path ch11/11.13/11.13.2/S11.13.2_A4.5_T2.8.js
+ * @description Type(x) is different from Type(y) and both types vary between Boolean (primitive or object) and Undefined
+ */
+
+//CHECK#1
+x = true;
+x -= undefined;
+if (isNaN(x) !== true) {
+  $ERROR('#1: x = true; x -= undefined; x === Not-a-Number. Actual: ' + (x));
+}
+
+//CHECK#2
+x = undefined;
+x -= true;
+if (isNaN(x) !== true) {
+  $ERROR('#2: x = undefined; x -= true; x === Not-a-Number. Actual: ' + (x));
+}
+
+//CHECK#3
+x = new Boolean(true);
+x -= undefined;
+if (isNaN(x) !== true) {
+  $ERROR('#3: x = new Boolean(true); x -= undefined; x === Not-a-Number. Actual: ' + (x));
+}
+
+//CHECK#4
+x = undefined;
+x -= new Boolean(true);
+if (isNaN(x) !== true) {
+  $ERROR('#4: x = undefined; x -= new Boolean(true); x === Not-a-Number. Actual: ' + (x));
+}
+