Nasus Wither Stops Malphite Ult

In my previous game I was Malphite Top against Nasus top. The first time their jungle came to gank i did not get withered and i escaped with my ult. The second time, however, i was withered. I spammed r trying to get away with ult, but this was to no avail. I thought maybe it was just a one time thing so I decided that i would try to test it out. The third time they went in for the gank i stayed with nasus until he withered me and then tried to ult out and again nothing would happen. I don't know if any other characters abilities are affected while they are withered by nasus but hopefully this gets corrected soon. Thank you for reading, enjoy your day.