opaque doesn't count if root of lowerdir

gistfile1.txt

root@bincastle-dev:/home/sipsma/tmp/test-opq# ls
1  2  merged
root@bincastle-dev:/home/sipsma/tmp/test-opq# ls *
1:
foo

2:
foo

merged:
root@bincastle-dev:/home/sipsma/tmp/test-opq# ls {1,2}/foo
1/foo:
1

2/foo:
2
root@bincastle-dev:/home/sipsma/tmp/test-opq# xattr {1,2}/foo
1/foo: trusted.overlay.opaque
2/foo: trusted.overlay.opaque
root@bincastle-dev:/home/sipsma/tmp/test-opq# mount overlay -t overlay -o lowerdir=1:2 merged/
root@bincastle-dev:/home/sipsma/tmp/test-opq# ls merged/
foo
root@bincastle-dev:/home/sipsma/tmp/test-opq# ls merged/foo/
1
root@bincastle-dev:/home/sipsma/tmp/test-opq# umount merged
root@bincastle-dev:/home/sipsma/tmp/test-opq# mount overlay -t overlay -o lowerdir=1/foo:2/foo merged/
root@bincastle-dev:/home/sipsma/tmp/test-opq# ls merged/
1  2