Lockscreen soft keys missing?

Jan 8, 2014
I can't remember since which version, after update to the 13.12.27 version on my Nexus 4, it seems the 'home' and 'back' soft keys are gone, only 'menu' is still there. I don't know is it meant to be like that or a bug? without the home button, I can't access the torch function without unlock the device. So does anyone else have the same issue? Thank you!