Image Sequence texture - Can't load image

When I try to add Image Sequence texture, I allways get a message "Can’t Load Image: Frame:1.
But, when I change Offset slider from 0 to anything else, it loads Image Sequence texture just fine. And it keeps working when I switch Offset back to 0.
Is this a bug or some feature?
The same happens with 2.62 and 2.63