Should throw TypeError Instead of Returning [object]

[JitCompiler]

When trying to convert an object which has no "toString()" nor "valueOf()" method to string, the ECMAScript 5.1 spec specifies the js system should throw a TypeError exception (point 5 below). Testing shows that mujs returns the string "[object]" instead. Is it an intended non-standard behaviour?

The relevant paragraphs of the ECMAScript 5.1 spec are here:

8.12.8 [[DefaultValue]] (hint)
When the [[DefaultValue]] internal method of O is called with hint String, the following steps are taken:
1. Let toString be the result of calling the [[Get]] internal method of object O with argument "toString".
2. If IsCallable(toString) is true then,
a. Let str be the result of calling the [[Call]] internal method of toString, with O as the this value and
an empty argument list.
b. If str is a primitive value, return str.
3. Let valueOf be the result of calling the [[Get]] internal method of object O with argument "valueOf".
4. If IsCallable(valueOf) is true then,
a. Let val be the result of calling the [[Call]] internal method of valueOf, with O as the this value and
an empty argument list.
b. If val is a primitive value, return val.
5. Throw a TypeError exception