wheel_up event lost after setupMouse in other panda window

Hi, I have two panda windows, one is default, and the other is open with base.openWindow. Since I want mouse control on the second window, i used base.setupMouse(base.winList[1]). The problem is, it can detect the mouse1, mouse2, … events, but not wheel_up and wheel_down event. I try to find the showbase source, and I can’t find anything wrong with the code. How to enable the wheel_up and wheel_down event?