That works, or you can knit the tail together for the first few stitches very tightly. Some people like to cast on an extra stitch and then k2to to close at first, but I find I still get a stretch this way. Here's what I have found gives the MOST perfect and invisible join:
Switch the first and last stitch in place. So the first caston stitch goes onto the needle beside the last stitch. Now use a crochet hook to pull that last stitch off its needle and onto the other needle, where the first stitch used to be before you moved it. They have now switched places. (Or you can move the last stitch to be next to the first, and then hook the first off onto the other needle, doesn't matter which) and knit the first few stitches tightly just to be sure.