The other solution is to overlap by 1px instead of placing exactly adjacent. I'd point out you'd have this same problem in any engine that implements spritesheeting.
Maybe there's a way to avoid the spritesheet of current object? The 1px displacement is not gonna work because i have a physics game where you got to build the level, and even if the sprites lost 1px on edge, the collision poly remains the same, and the displacement will make something like this (red lines is the collision polygon). This will make the level unplayable.
[attachment=0:33pd4r5z][/attachment:33pd4r5z]
I tried to make my puzzle-like level parts bigger (2000x2000) so they don't export to spritesheet, and then after export crop the images and compile the project, but this is not working, because that was a stupid idea i guess