ALAssetsLibrary returning nil for asset that has HEIC URL

Question

I'm using ALAssetsLibrary to grab an image using its assets library URL. This works fine if the image is a jpeg. However, if I try and grab one that is an HEIF, the call returns nil for the asset. I know that I will need to convert to using PHPhotoLibrary at some point but I'm not quite ready for that yet. Anybody ever seen this problem and/or know how to get around it? Is ALAssetsLibrary just not compatible with HEIF? Here's some code:

let library = ALAssetsLibrary()
// url is set elsewhere
library.asset(for: url, resultBlock: { (asset) in
    // asset is nil here if I pass in an HEIC url, fine if it is JPEG
    // "assets-library://asset/asset.HEIC?id=070FBF77-869D-4B3D-840A-74B4FC65648D&ext=HEIC"
}, failureBlock: { (error) in 
    // Handle error
})