diff --git a/lib/OpenLayers/Layer/Grid.js b/lib/OpenLayers/Layer/Grid.js
index 80981a1b1a..1f8a174f9d 100644
--- a/lib/OpenLayers/Layer/Grid.js
+++ b/lib/OpenLayers/Layer/Grid.js
@@ -146,14 +146,16 @@ OpenLayers.Layer.Grid.prototype =
                 this._initTiles();
             } else {
                 while (true) {
-                    var topLeft = this.map.getViewPortPxFromLayerPx( this.grid[0][0].position );
-                    if (topLeft.x > -this.tileSize.w * (this.buffer - 1)) {
+                    var tlLayer = this.grid[0][0].position;
+                    var tlViewPort = 
+                        this.map.getViewPortPxFromLayerPx(tlLayer);
+                    if (tlViewPort.x > -this.tileSize.w * (this.buffer - 1)) {
                         this.shiftColumn(true);
-                    } else if (topLeft.x < -this.tileSize.w * this.buffer) {
+                    } else if (tlViewPort.x < -this.tileSize.w * this.buffer) {
                         this.shiftColumn(false);
-                    } else if (topLeft.y > -this.tileSize.w * (this.buffer - 1)) {
+                    } else if (tlViewPort.y > -this.tileSize.w * (this.buffer - 1)) {
                         this.shiftRow(true);
-                    } else if (topLeft.y < -this.tileSize.h * this.buffer) {
+                    } else if (tlViewPort.y < -this.tileSize.h * this.buffer) {
                         this.shiftRow(false);
                     } else {
                         break;