Moving Platforms in side scrolling platform game

Hi, I’ve been working on a sidescrolling platform game and just recently added a level with moving platforms- they go up and down. My gravity function has been working fine with the ground not going anywhere but as soon as the sprite stands on a moving platform in falls through.

This is what my gravity looks like, all the actionscript is on the main sprite mc:

if (_root.groundlevel4.platformlevel4.hitTest(this._x, this._y, true) && falling) {
jump = 8;
jumping = false;
falling = false;

}

“groundlevel4” is everything on the ground, dirt, rocks, etc, and “platformlevel4” is the mc inside of “groundlevel4” that is just the grass or moving platforms. aka things that the sprite can stand on.

any suggestions???

Thanks!