Cartographer Villager doesn't have an EXP bar even though it has a claimed workstation

I updated my village-centric game from 1.8 to snapshot 1.9, and to accommodate the new villager's mechanics I placed beds and workstations around the village. This cartographer was the only villager to stay, and it has a claimed workstation, but it doesn't have an EXP bar to grow in its profession. Is this a (known) bug or am I doing something wrong?