Disable camera pitch axis/rotation

I would like to completly disable rotation (pitch axis) of the camera. Is there a method to do it in Cesium camera object? I have tried to set “scene.camera.constrainedAxis = Cesium.Cartesian3.UNIT_Z” but it doesn’t work for me. There is one example in the sandcastle with postUpdate handler 9689. The example works weird when I change condition to (dotProduct >= -0.9999), but I don’t need to limit tilt, I just want to disable pitch axis completly. This use case is only for the mobile users. User should be able only to zoom in/out, move on the map and should be able to change yaw axis (heading).