Strange behavior with the up,left,space bar key combo

I was checking if the up and left arrow and the space bar was pressed in my game code to allow the player to move and turn and shoot at the same time. Turns out that in GameMaker 7, if the user holds up+left+space bar keys at the same time, either the up or the left arrow key event will be ignored. I had to change the shoot key to the key to go around this weird behavior.