Why did Yosef make them swear?

Parshat Va'Yechi

We know why Yaakov made Yosef swear to bury him in Eretz Yisrael rather than Egypt, as the meforshim tell us a number of reasons, mainly to allow Yosef an excuse for Par'oh why he had to do it (meaning Par'oh would try to convince Yosef to not go and Yosef would say I swore and if I do not keep my oath, I do not need to keep my oath to you either).
At the end of the parsha, Yosef is dying and calls in his brothers and makes them swear that they will remove his bones and take them to Eretz Yisrael. Why did he need to make them swear? Could he not rely on them to do it for him without an oath?

I do not at this point have a satisfactory explanation.