SCNRenderer does not produce depth texture with SCNLight inside scene

I use SCNRenderer to render SCNScene in my custom rendering pipeline. Also, I need to retrieve scene depth texture during rendering. I do it with:

Code Block Swift
passDescriptor.depthAttachment.texture = depthTexture
passDescriptor.depthAttachment.clearDepth = 1.0
passDescriptor.depthAttachment.loadAction = .clear
passDescriptor.depthAttachment.storeAction = .store

Everything works as expected, I do receive scene depth texture. But when I add a directional SCNLight with .castsShadow = true property into my scene, SCNRenderer writes zeros into depth texture.

Code Block Swift
let lightNode = SCNNode()
lightNode.light = SCNLight()
lightNode.light?.type = .directional
lightNode.light?.castsShadow = true
//...

After adding .castsShadow = true entire depth texture is filled up with zeros. But when I comment out .castsShadow = true line, depth texture works as expected. I can't understand why does it happen.

My current solution:
I now use 2 scenes: with and without light. The first one I use to retrieve the picture of my scene and the second one I use to retrieve the depth of my scene. But I think it's not the best solution and there must be a better way to deal with this problem.

Are there any ideas where I should be looking?

I use MetalKit only (no OpenGL) in my project.
Device: iPhone 12 Pro
OS: iOS 14.2
Xcode: 12.1