Pale oak affecting zombies and skeletons

While playing on my world I had villagers inside of a building made with the new pale oak planks. During the night a zombie got in and converted them, while getting the items to cure them they burned up from sunlight inside the building. Was confused by why they died that way, so I waited till night and got regular zombies and locked them inside the same building and waited till day and saw that they also burst into flames like they do outside. The entire roof is filled in and there is no open holes for sunlight, I belive that pale oak planks are being considered to be transparent in the code.