Gauge - help!

I have a fairly simple, and probably a bit stupid, question about gauge. The pattern I want to knit says that my gauge should be 20 stitches and 32 rows equalling 4 inches. But, while my width (nr of stitches) is about 4 inch/10cm, by length is way longer, around 13cm . I was now wondering what exactly I could do about this? I can’t take smaller size needles because then my widt is not 4 inch anymore. I don’t want to take other wool.
Is there something else I could do to have a correct gauge swatch?

Try a smaller needle, it may affect your rows more than your stitches. And it’s better to CO about 30 sts with 5 on each side in an edging and measure the 20 sts in the middle. Also knit several rows before making the 32 rows. The CO and edge sts aren the same size as a regular stitch and row so you need a few more to measure accurately. If that doesn’t work then don’t worry about the rows, most people don’t get gauge and typically patterns are written to knit X inches, not X rows.