Default [Q] Xperia U got unrooted after automatic Cyanogen system update


Since about one year I successfully run the Cyanogen 11 on my Xperia U from here

Originally, I had rooted the device but after one of the last automatic updates of Cyanogen (unfortunately I didn't observe which one exactly this was) I lost root access.
What happend? How do I get root back.

Current versionn is 11-20140817-UNOFFICIAL-kumquat, Android 4.4.4, Kernel 3.0.101_by_Munjeni_and_XperiaSTE-g83ded76.