squashfs operation not supported

I am creating customized install cd. As part of process I need to unsquashfs existing filesystem.squashfs, add few files and then recreate filesystem (mksquashfs).

Seems that everything is working, but... I see 'Operation not supported' error/warning in syslog for every file/directory in filesystem. How can I fix this error/warning?

Small part from syslog:

...
base-installer: info: Using squashfs support for /cdrom/install/filesystem.squashfs
anna-install: Installing squashfs-modules
anna[21857]: DEBUG: resolver (kernel-image-4.2.0-16-generic-di): package doesn't exist (ignored)
anna[21857]: DEBUG: retrieving squashfs-modules-4.2.0-16-generic-di 4.2.0-16.19
kernel: [44.008353] squashfs: version 4.0 (2009/01/31) Phillip Lougher
main-menu[3537]: (process:21801): getfattr: .: Operation not supported
main-menu[3537]: (process:21801): getfattr: ./bin: Operation not supported
main-menu[3537]: (process:21801): getfattr: ./bin/bunzip2: Operation not supported
main-menu[3537]: (process:21801): getfattr: ./bin/bzcat: Operation not supported
main-menu[3537]: (process:21801): getfattr: ./bin/bzcmp: Operation not supported
...