aframe: setAttribute position doesn't work

I just tried to get an a-image and set its position via setAttribute, and the position isn’t taken into account

var aScene = document.querySelector("a-scene");
var img = document.createElement("a-image");
aScene.appendChild(img);
img.setAttribute('position', {x:0,y:2,z:0});

• A-Frame Version: the last one top of tree in /dist
• Platform/Device: windows 10 and google chrome 50