In one terminal
$ GNUTLS_DEBUG_LEVEL=6 ./httpfs2-ssl -f http://localhost ~/t/mnt
...
httpfs2-ssl: httpfs2.c:352: httpfs_read: Assertion `url->file_size >= off' failed.
In other terminal:
$ dd if=$HOME/t/mnt/localhost count=1 bs=80 skip=1000
dd: /home/porton/t/mnt/localhost: cannot skip to specified offset
dd: error reading '/home/porton/t/mnt/localhost': Software caused connection abort
0+0 records in
0+0 records out
0 bytes copied, 0.077479 s, 0.0 kB/s
The content of http://localhost is attached.