btrfs-progs: btrfs-convert: unable to find block group for 0

[Tucker Boniface]

Hello, I am trying to convert an ext4 partition to btrfs using 
btrfs-convert. I am running Arch Linux with kernel 4.18.5 and 
btrfs-progs 4.17.1. The full error is inline below.

-> # btrfs-convert /dev/sda1
create btrfs filesystem:
        blocksize: 4096
        nodesize:  16384
        features:  extref, skinny-metadata (default)
creating ext2 image file
Unable to find block group for 0
Unable to find block group for 0
Unable to find block group for 0
extent-tree.c:2743: alloc_tree_block: BUG_ON `ret` triggered, value -28
btrfs-convert(+0x1d512)[0x564d08cd3512]
btrfs-convert(btrfs_alloc_free_block+0x1e8)[0x564d08cda188]
btrfs-convert(+0x15bd1)[0x564d08ccbbd1]
btrfs-convert(btrfs_search_slot+0xf27)[0x564d08ccd7d7]
btrfs-convert(btrfs_csum_file_block+0x499)[0x564d08cdf219]
btrfs-convert(+0xe625)[0x564d08cc4625]
btrfs-convert(main+0x1abf)[0x564d08cc3adf]
/usr/lib/libc.so.6(__libc_start_main+0xf3)[0x7f1822576223]
btrfs-convert(_start+0x2e)[0x564d08cc41be]
Aborted