The constructor properties on the prototypes of error objects should...

src/messages.js

Index: src/messages.js
===================================================================
--- src/messages.js	(revision 435)
+++ src/messages.js	(working copy)
@@ -639,8 +639,8 @@
   // prototype of 'Error' must be as default: new Object().
   if (name != 'Error') %FunctionSetPrototype(f, new $Error());
   %FunctionSetInstanceClassName(f, 'Error');
+  %SetProperty(f.prototype, 'constructor', f, DONT_ENUM);
   f.prototype.name = name;
-  f.prototype.constructor = f;
   %SetCode(f, function(m) {
     if (%IsConstructCall()) {
       if (!IS_UNDEFINED(m)) this.message = ToString(m);