Please file a bug about this specific case (system r/o NTFS driver blocks r/w FSKit driver) and then post that bug number back here. I have filed a bug: FB18230524 You might also try including "-t nontfs". I haven't tried it, but I believe that would exclude the kernel NTFS driver while leaving yours as an option. It looks like mount (without -F) tries to use literal non-existent nontfs filesystem in this case: $ mount -t nontfs disk2s2 ./mnt mount: exec /Library/Filesystems/nontfs.fs/Contents/Resources/mount_nontfs for /Users/user/temp/fstest/mnt: No such file or directory mount: /Users/user/temp/fstest/mnt failed with 72 You ran "mount" as root, correct? I currently run mount as a normal administrator user (otherwise this workaround would need a helper with elevated privileges to be used in the app). However, I also attempted to run it as root. In that case the mount -F command fails without providing a specific error message. $ sudo mount -F -t abcd_ntfs disk11 ./mnt mount: Unable to invoke task # mount -F -t abcd_ntfs disk11 ./mnt mount: Unable to invoke task Judging by the logs, it stops somewhere early: default 16:54:13.664228+0200 fskitd Hello FSClient! entitlement no default 16:54:13.664465+0200 mount Setting remote protocol to all XPC default 16:54:13.665000+0200 fskitd Getting own modules default 16:54:13.665045+0200 fskitd Returning module array <private> default 16:54:13.665236+0200 mount [0x7fe9e1a04140] invalidated because the current process cancelled the connection by calling xpc_connection_cancel() default 16:54:13.665266+0200 fskitd [0x7f9424a05570] invalidated because the client process (pid 1542) either cancelled the connection or exited Furthermore, the mount -F command fails for all volumes when run with root privileges, including non-physical volumes. Is the slice you're trying to target on the boot device or is it an external volume? I have tested both a volume on the boot device and an external volume on a USB device. In both cases, the same error occurs and almost identical logs: $ mount -F -t abcd_ntfs disk2s2 ./mnt mount: Probing resource: The operation couldn’t be completed. Permission denied mount: Unable to invoke task Are you able to mount disk images? Yes, disk images can be mounted without issues using the non-root mount -F command. $ hdiutil attach -imagekey diskimage-class=CRawDiskImage -nomount ./ntfs-rw.dmg /dev/disk11 $ mount -F -t abcd_ntfs disk11 ./mnt $ diskutil info disk11 Device Identifier: disk11 Device Node: /dev/disk11 Whole: Yes Part of Whole: disk11 Device / Media Name: Disk Image Volume Name: NTFS_IMAGE Mounted: Yes Mount Point: /Users/user/temp/fstest/mnt Finally, I'm not sure how the NTFS collision changes things. Just in case, the filesystem short name in my FSKit module is not ntfs/NTFS to avoid the naming collision. The big thing to look at here is what the large system log shows, particularly between these log messages: I have attached fuller log of that area. FSKit log