In a fluid coking process in which coke from the coker is passed to a heater and then to a gasifier and in which part of the heat for the heater is supplied by the gases from the gasifier, ungasified coke from the bottom of the gasifier is conveyed through a riser to the heater to supply additional heat and thence back to the coker whereby strength of the coke is increased by fresh coke deposition and in which all the oxygen is injected into the lower gasifier bed thereby eliminating possibility of oxygen breakthrough. The same results can be accomplished by passing the coke from the gasifier directly back to the coke reactor and eliminating the coke stream from the upper heater bed to the reactor.