Why doesn't PIL/Pillow crop work?

I'm trying to use Pillow to crop an image, but it doesn't seem to work. I've got the following code:

im = Image.open('the_image.jpg')
print 'ORIGINAL SIZE: ', im.size
im.crop((1087, 0, 1820, 2197))
print 'CROPPED SIZE: ', im.size

which prints this in the terminal:

ORIGINAL SIZE:  (2908, 2197)
CROPPED SIZE:  (2908, 2197)

Does anybody know why the cropping doesn't seem to work? All tips are welcome!