If so, watch your hands on the way down. Don't bend your arms. Use your stomach and back muscles. Don't kick over until your hands touch the ground. Do them over a mailbox mat until you're comfortable or with a spot.
If you can't do a kickover, work them until you can do them very well before starting walkovers.
I agree with the above posts. My kids that have a kickover that have trouble with a walkover often try to put too much weight on the front leg (you shouldn't put any weight on it). That makes your hips go forward and stops the kickover motion. If you can kickover from a backbend, then try resting your heel on top of something 6-8 inches off the ground. Always wait until your hands touch to kick or you'll end up on your head!