ASP.NET Usercontrol inside another Usercontrol not firing javascript code

ASP.NET Usercontrol inside another Usercontrol not firing javascript code

I haver a usercontrol inside another usercontrol and i'm registering a
javascript function by this way :
ScriptManager.RegisterStartupScript(this, typeof(Page),
UniqueID, "alert('hi')", true);
but the script is not firing.. someone knows why?