Game Maker for Beginners: Part III

I am having difficulty keeping the ship on the screen. I'm pretty sure I've done everything correctly. It's coded into the step event of oPlayerShip. The ship does seem to slow down when it reaches the edge, but it will still go off the screen. Now, I did set oPlayerShip's movement to speedUP, so that I could just change the value of speedUP to whatever I wanted for testing purposes. Does anyone have any idea where the problem could be?

I am loving this tutorial though, regardless the age it's been awesome so far.