Naturally generated stationary lava doesn't update

When an air block is near a naturally gen. stationary/not moving lava block it don't flows to the air block instead, it stays as if nothing happened.
To reproduce, find naturally generated lava(mostly found in deep caves),then make the block adjacent to it an air block this is either done by mining the block if it's soild or if it's lava/liquid block by the lava use a bucket.