[Samba] writable share with guest acount problem

[GNUtoo at no-log.org]

here's my smb.conf
# Uncomment this if you want a guest account, you must add this to
/etc/passwd
# otherwise the user "nobody" is used
;  guest account = pcguest
# Allow users to map to guest:
  map to guest = bad_user

i have the bad_user and the nobody user in my unix acounts:
bad_user:x:1007:1014:bad_user:/:/bin/false
nobody:x:65534:65534:nobody:/:/bin/false

but when i mount the share it says:
doing parameter map to guest = bad user

and i can't write to the share(even if i use my samba username and password)

but i can write to shares that requires an autentification if i autentify