Tilde for relative commands doesn't work in target arguments

When a tilde (~) is put in an argument the command fails (e.g. /tp @p[x=~,y=~,z=~] x y z)

What I expected to happen was...:
Teleport closest player to location

What actually happened was...:
Output to console:
That player could not be found

Steps to Reproduce:
1. Type a console command with either @p, @a, @r with a x, y of z argument with a tilde in it.