In Messerschmitt Bf 109 F, G & K Series, by Prien and Rodeike, the chapter on the K-4 mentions that some were delivered with an MG 151/20 hub cannon.
Wrongway, wikipedia articles are as accurate as their citations. Good citations make for good articles, and the 109 article seems to set a high standard. Check out the talk page and you can see the other users lay the smack down on "kurtfurst."