That is called "laddering". I have seen some folks suggest moving the stitches to the cable of the first needle before starting the second needle and pulling the first couple of stitches extra tight.
I'm doing a pair of socks on 1 long circ using Magic Loop, and I'm not experiencing any laddering (I did get ladders when I used 2 circs).
Even if you can't eliminate all the laddering while knitting, most of the extra space will distribute with washing and wear. More than likely it will not be noticeable later on.