Fire Spreading further than expected

I have built a big house and a fire pit on a server and while building this house the floor plans called for a fire pit. Only problem is coming back to the house later the entire upper floors were on fire. A picture of the pit is I also built a similar version in survival and it does the same things the blocks set on fire even though they are blocked by roofs and not touching.

Not sure if this is a bug or if the fire was changed to jump to wood 6 blocks away from its source. the fire is on nether rack if that has any thing to do with how the fire is spreading.