Rebellion bug...maybe

I capture a province. While in the province I upgrade a unit. The upgrade takes 3 hours. All other units leave the province except the upgrading unit. Day changes with the unit upgrading. It rebels to a country I am at peace with but as soon as the upgrading is complete the province switches back to my country causing me to be at war.

I would think either:

A) The province should not rebel since I have units garrisoning the province (even though upgrading).

B) The province should immediately rebel at turn of day because the game does not recognize upgrading units as garrisoned units.

Am i missing something?