Error on FAT32

[Removed by request]

I'm using Ubuntu 15.04 dev with secure-delete 3.1-6ubuntu1 and on wiping the empty space of an USB flash drive with FAT32 as filesystem I'm always getting this error after several hours:

root@ubuntu:~# sfill -fllv /media/sdf1
Wipe mode is insecure (one pass [random])
Wiping now ...
Creating /media/sdf1/oooooooo.ooo ... * Wiping inodes ...sfill: malloc.c:2372: sysmalloc: Assertion `(old_top == (((mbinptr) (((char *) &((av)->bins[((1) - 1) * 2])) - __builtin_offsetof (struct malloc_chunk, fd)))) && old_size == 0) || ((unsigned long) (old_size) >= (unsigned long)((((__builtin_offsetof (struct malloc_chunk, fd_nextsize))+((2 *(sizeof(size_t))) - 1)) & ~((2 *(sizeof(size_t))) - 1))) && ((old_top)->size & 0x1) && ((unsigned long) old_end & pagemask) == 0)' failed.
Aborted

Also the filesystem does then contain several empty files with random filenames.

[Removed by request (removed3425744)]

Also I'm noticing if I'm targeting the device file I'm getting 2 errors while the second looks it should not appear:

root@ubuntu:~# sfill -fllv /dev/sdf1
Error: /dev/sdf1 is not a directory
Programming Error: sdel-lib was not initialized before calling sdel_finnish().

[Kenneth Wrede (kennethwrede)]

I got the same error.
Programming Error: sdel-lib was not initialized before calling sdel_finnish()

So it is about file systems? It should better tell if it is an unsupported one.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.