--- a/mobile/chrome/content/input.js
+++ b/mobile/chrome/content/input.js
@@ -323,18 +323,21 @@ MouseModule.prototype = {
       //
       let [sX, sY] = dragData.panPosition();
       this.dX += dragData.prevPanX - sX;
       this.dY += dragData.prevPanY - sY;
 
       if (dragData.isPan()) {
         // Only pan when mouse event isn't part of a click. Prevent jittering on tap.
         this._kinetic.addData(sX - dragData.prevPanX, sY - dragData.prevPanY);
-        this._dragBy(this.dX, this.dY);
-        // dragBy will reset dX and dY values to 0.
+        if (!this._waitingForPaint) {
+          this._dragBy(this.dX, this.dY);
+          this.dX = 0;
+          this.dY = 0;
+        }
 
         // Let everyone know when mousemove begins a pan
         if (!oldIsPan && dragData.isPan()) {
           this._mouseOverTimeout.clear();
           this._longClickTimeout.clear();
 
           let event = document.createEvent("Events");
           event.initEvent("PanBegin", true, false);
@@ -386,26 +389,21 @@ MouseModule.prototype = {
 
   /**
    * Used by _onMouseMove() above and by KineticController's timer to do the
    * actual dragMove signalling to the dragger.  We'd put this in _onMouseMove()
    * but then KineticController would be adding to its own data as it signals
    * the dragger of dragMove()s.
    */
   _dragBy: function _dragBy(dX, dY, aIsKinetic) {
-    let dragged = true;
-    if (!this._waitingForPaint || aIsKinetic) {
-      let dragData = this._dragData;
-      dragged = this._dragger.dragMove(dX, dY, this._targetScrollInterface, aIsKinetic);
-      if (dragged && !this._waitingForPaint) {
-        this._waitingForPaint = true;
-        mozRequestAnimationFrame(this);
-      }
-      this.dX = 0;
-      this.dY = 0;
+    let dragData = this._dragData;
+    let dragged = this._dragger.dragMove(dX, dY, this._targetScrollInterface, aIsKinetic);
+    if (dragged && !this._waitingForPaint) {
+      this._waitingForPaint = true;
+      mozRequestAnimationFrame(this);
     }
     return dragged;
   },
 
   /** Callback for kinetic scroller. */
   _kineticStop: function _kineticStop() {
     // Kinetic panning could finish while user is panning, so don't finish
     // the pan just yet.