Can't use DocumentsContract.getDocumentId on uri gotten from ActivityResultContracts.OpenDocumentTree()

Question

From here: https://stackoverflow.com/a/70933975/13519865

if I,

private val dirRequest = registerForActivityResult(ActivityResultContracts.OpenDocumentTree()) { uri ->
    if (uri != null) {

DocumentsContract.getDocumentId(uri)

}

}

I get

java.lang.IllegalArgumentException: Invalid URI: content://com.android.externalstorage.documents/tree/9C33-6BBD%3AA
at android.provider.DocumentsContract.getDocumentId(DocumentsContract.java:1278)

I need documentId for,

DocumentsContract.buildChildDocumentsUriUsingTree(rootUri, documentId)