vbs脚本中创建“WScript.Shell”对象出现800A01B6错误

vbs脚本中创建“WScript.Shell”对象出现800A01B6错误,并提示“对象不支持此属性或方法”

出错脚本:
Dim WshShell
WshShell = CreateObject("WScript.Shell")
WshShell.Run "xxx"

修改为,问题消失:
Dim WshShell
Set WshShell = CreateObject("WScript.Shell")
WshShell.Run "xxx"

语法问题!