FLOAT pass target isn't working

[tdhooper]

I'm trying to use a FLOAT render target:

/*{
    "ISFVSN": "2",
    "INPUTS": [],
    "PASSES": [
        {
            "TARGET": "pass0",
            "FLOAT": true
        },{
            "DESCRIPTION": "Render"
        }
    ]
}*/

void main() {
    if (PASSINDEX == 0) {
		gl_FragColor = vec4(1,0,0,1);
    } else {
    	gl_FragColor = IMG_NORM_PIXEL(pass0, gl_FragCoord.xy / RENDERSIZE);
    }
}

This shows a black screen, removing the FLOAT shows a red screen.