--- a/mobile/chrome/content/InputHandler.js
+++ b/mobile/chrome/content/InputHandler.js
@@ -330,17 +330,17 @@ ChromeInputModule.prototype = {
 
     aEvent.stopPropagation();
     aEvent.preventDefault();
 
     let dx = dragData.sX - aEvent.screenX;
     let dy = dragData.sY - aEvent.screenY;
 
     if (!dragData.dragging && dragData.dragStartTimeout != -1) {
-      if ((Math.abs(dx*dx) + Math.abs(dy*dy)) > 100) {
+      if (dx*dx + dy*dy > 100) {
         clearTimeout(dragData.dragStartTimeout);
         this._dragStart(aEvent.screenX, aEvent.screenY);
       }
     }
     if (!dragData.dragging)
       return;
 
     this._dragMove(aEvent.screenX, aEvent.screenY);
@@ -541,17 +541,17 @@ ContentPanningModule.prototype = {
       return;
 
     let dragData = this._dragData;
 
     let dx = dragData.sX - aEvent.screenX;
     let dy = dragData.sY - aEvent.screenY;
 
     if (!dragData.dragging && dragData.dragStartTimeout != -1) {
-      if ((Math.abs(dx*dx) + Math.abs(dy*dy)) > 100) {
+      if (dx*dx + dy*dy > 100) {
         clearTimeout(dragData.dragStartTimeout);
         this._dragStart(aEvent.screenX, aEvent.screenY);
       }
     }
     if (!dragData.dragging)
       return;
 
     this._dragMove(aEvent.screenX, aEvent.screenY);