cudnn v2 cudnnPoolingBackward

Hi all,
I have a test:

5 SAME images
1 channels
6 * 6 size of images

pooling window = 3
v and h paddings = 0
v and h strides = 1

And after cudnnPoolingBackward for each image I see the same result except the last value of the last image (which is zero).
Is it bug?