Spidermonkey Embedding: How Can I Set Class Properties?

I am embedding Spidermonkey in a C app. and I'm having trouble setting
class (not instance) property values. For example, I am setting up
the class as follows:

static JSBool constructor(JSContext *cx, JSObject *obj, uintN argc, jsval
*argv, jsval *rval)
{
printf("constructor argc = %d
", argc);
*rval = OBJECT_TO_JSVAL(obj);
return JS_TRUE;
}

main()
{
....
static JSClass my_class = {
"MyClass", JSCLASS_HAS_PRIVATE,
JS_PropertyStub,JS_PropertyStub,JS_PropertyStub,JS _PropertyStub,
JS_EnumerateStub,JS_ResolveStub,JS_ConvertStub,JS_ FinalizeStub
};
static JSPropertySpec class_props[] = {
{"Prop1", 0, JSPROP_ENUMERATE},
{0}
};
JSObject *proto;

proto = JS_InitClass(cx, JS_GetGlobalObject(cx), 0, &my_class,
constructor, 1, NULL, NULL, class_props, NULL);

The above code correctly (verified through a JavaScript program). creates a new class with the Prop1 class property.

The following code correctly adds an _instance_ property:

jsval val = INT_TO_JSVAL(42);
JS_SetProperty(cx, proto, "MyProp2", &val);

After three days I still can't figure out how to set the value of the class
property, or, for that matter, create a new class property with a particular value. I am looking to do something like this:

jsval val = INT_TO_JSVAL(88);
JS_SetProperty(cx, ???, "Prop1", &val);