Animate exports in 16:9 format instead of 4:3

I'm creating an animated segment for a trailer in a game I am making, and I apparently ran into a problem with it. With all the other trailers, they exported fine in the intended 4:3 aspect ratio, but when it came time to export my newest animation, it apparently exported in 16:9 format instead of the 4:3 format that was intended. I tried numerous times and I kept getting the same result. Is there anything I am doing wrong?