Zoom issue with latest version of library - fabricjs

Question

The below code snippets are identical, except for the version of FabricJS being used.
The first one uses version 1.4.13, the second uses the latest (1.7.3).
When clicking Zoom In on the first version, the black square remains exactly top-left (0, 0). So far, so good.
When doing the same on the second version, the black square "drifts" where you can see the pink background above and to the left of the black square.
Does anyone why this behaviour has changed, is there a workaround or other fix?
var canvas = new fabric.Canvas('c');
canvas.setBackgroundImage('http://placehold.it/640x480/dd0055/?text=FabricJS Demo', canvas.renderAll.bind(canvas), {
backgroundImageOpacity: 0.5,
backgroundImageStretch: false
});
canvas.add( new fabric.Rect({
left: 0,
top: 0,
width:100,
height:100,
fill:"rgb(0,0,0)"
}) );
canvas.renderAll();
$("#btnZoomIn").click(function(){
canvas.setZoom(canvas.getZoom()*1.3);
});
$("#btnZoomOut").click(function(){
canvas.setZoom(canvas.getZoom()/1.3);
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/fabric.js/1.4.13/fabric.min.js"></script>
<button id="btnZoomIn">ZoomIn</button>
<button id="btnZoomOut">ZoomOut</button>
<br/>
<canvas id="c" width="640" height="480"></canvas>
var canvas = new fabric.Canvas('c');
canvas.setBackgroundImage('http://placehold.it/640x480/dd0055/?text=FabricJS Demo', canvas.renderAll.bind(canvas), {
backgroundImageOpacity: 0.5,
backgroundImageStretch: false
});
canvas.add( new fabric.Rect({
left: 0,
top: 0,
width:100,
height:100,
fill:"rgb(0,0,0)"
}) );
canvas.renderAll();
$("#btnZoomIn").click(function(){
canvas.setZoom(canvas.getZoom()*1.3);
});
$("#btnZoomOut").click(function(){
canvas.setZoom(canvas.getZoom()/1.3);
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/fabric.js/1.7.3/fabric.min.js"></script>
<button id="btnZoomIn">ZoomIn</button>
<button id="btnZoomOut">ZoomOut</button>
<br/>
<canvas id="c" width="640" height="480"></canvas>

Answer 1

Being the main difference after fabric 1.5 the inclusion of strokeWidth in the object bounding box, i guess that if you initialize the fabric.Rect with strokeWidth: 0 OR with a stroke: 'blue' you will se that the object is not drifting, simply is moving from is left top corner.
What cause the drift is a transparent border that is growing in size.