r=65536 in command block doesn't work anymore

You used to be able to use a range of 65536 to get a range area of 1 block, because 65536 is an intentional integer overflow. For example: if you use a command block programmed with

/testfor @p[x=10,y=11,z=12,r=65536]

, there will only be an output if the player is exactly in that block. This was the only way to get a range of 1 block.

Now, the overflow doesn't work anymore, you only get a ton of lag because the range is so big. Did the number to get the overflow change? Or is it totally removed? Or is there another way to get a range of 1 block? You also can't use r=0 or r=0.5 or something.