--- a/toolkit/content/widgets/browser.xml
+++ b/toolkit/content/widgets/browser.xml
@@ -1243,17 +1243,17 @@
             // autoscrolling on. So instead we do the same math as Gecko.
             const scaleFactor = 60 / Math.round(60 / screen.defaultCSSScaleFactor);
             let minX = left.value / scaleFactor + 0.5 * POPUP_SIZE;
             let maxX = (left.value + width.value) / scaleFactor - 0.5 * POPUP_SIZE;
             let minY = top.value / scaleFactor + 0.5 * POPUP_SIZE;
             let maxY = (top.value + height.value) / scaleFactor - 0.5 * POPUP_SIZE;
             let popupX = Math.max(minX, Math.min(maxX, screenX));
             let popupY = Math.max(minY, Math.min(maxY, screenY));
-            this._autoScrollPopup.openPopup(null, "after_start", popupX, popupY);
+            this._autoScrollPopup.openPopupAtScreen(popupX, popupY);
             this._ignoreMouseEvents = true;
             this._scrolling = true;
             this._startX = screenX;
             this._startY = screenY;
 
             window.addEventListener("mousemove", this, true);
             window.addEventListener("mousedown", this, true);
             window.addEventListener("mouseup", this, true);