Generated mesh depth error with Diffuse/Transparent shader

I have this blue mesh consisting of four quads (script-generated, Diffuse/Transparent shader). The light-blue quad should be behind the dark-blue quad on the front, but it isn't. It isn't an issue with dark blue quad's transparency, because another cube object hides behind it just fine.

I understand this has something to do with rendering order and is a problem that comes from using a Transparent shader. Indeed, when i use a non-transparent shader, everything works just fine.

Thing is, i really want to use a transparent shader for this object, so how do i go about fixing it without losing the transparent shader?