gio mount on localhost gives "permission denied"

I am trying to setup a local NFS server and mount it as well locally for file-manager testing purposes.

Mounting the mointpoint with mount works fine:

sudo mount 127.0.0.1:/home/schwinn/software/thunar_test /mnt/NFS_Test 

I can go to /mnt/NFS_Test, modify files, etc.

Though mounting it with gio mount gives me "permission denied":

Possibly this computer is not permitted or a privileged port is expected.

$ gio mount nfs://127.0.0.1:/home/schwinn/software/thunar_test
gio: nfs://127.0.0.1:0/home/schwinn/software/thunar_test:
Erlaubnis verwehrt: Möglicherweise ist dieser Rechner nicht zugelassen oder ein privilegierter Port wird erwartet

My /etc/exports has only a single line:

/home/schwinn/software/thunar_test 127.0.0.1(rw,sync,root_squash,subtree_check)

I as well tried with * and other attributes, though no luck so far.

I did sudo umount /mnt/NFS_Test before testing, restarted the service with sudo service nfs-kernel-server restart.

Any idea on how to further debug this would be welcome!