--- a/dom/base/nsDOMWindowUtils.cpp
+++ b/dom/base/nsDOMWindowUtils.cpp
@@ -3006,18 +3006,19 @@ nsDOMWindowUtils::SelectAtPoint(float aX
 
   // The root frame for this content window
   nsIFrame* rootFrame = presShell->FrameManager()->GetRootFrame();
   if (!rootFrame) {
     return NS_ERROR_UNEXPECTED;
   }
 
   // Get the target frame at the client coordinates passed to us
-  nsCOMPtr<nsIWidget> widget = GetWidget();
-  nsIntPoint pt(aX, aY);
+  nsPoint offset;
+  nsCOMPtr<nsIWidget> widget = GetWidget(&offset);
+  nsIntPoint pt = ToWidgetPoint(aX, aY, offset, GetPresContext());
   nsPoint ptInRoot =
     nsLayoutUtils::GetEventCoordinatesRelativeTo(widget, pt, rootFrame);
   nsIFrame* targetFrame = nsLayoutUtils::GetFrameForPoint(rootFrame, ptInRoot);
   // This can happen if the page hasn't loaded yet or if the point
   // is outside the frame.
   if (!targetFrame) {
     return NS_ERROR_INVALID_ARG;
   }

--- a/dom/tests/mochitest/chrome/selectAtPoint.html
+++ b/dom/tests/mochitest/chrome/selectAtPoint.html
@@ -159,18 +159,18 @@
                         .defaultView
                         .QueryInterface(Ci.nsIInterfaceRequestor)
                         .getInterface(Ci.nsIDOMWindowUtils);
 
     frame.contentWindow.scrollTo(0, 0);
 
     let rect = frame.getBoundingClientRect();
 
-    let targetPoint = { xPos: rect.left + (charDims.width / 2),
-                        yPos: rect.top + (charDims.height / 2) };
+    let targetPoint = { xPos: charDims.width / 2,
+                        yPos: charDims.height / 2 };
     setSingle(dwuFrame, targetPoint.xPos, targetPoint.yPos, Ci.nsIDOMWindowUtils.SELECT_WORDNOSPACE);
     checkSelection(frame.contentWindow.document, "SELECT_WORDNOSPACE", "ttestselection2");
     setSingle(dwuFrame, targetPoint.xPos, targetPoint.yPos, Ci.nsIDOMWindowUtils.SELECT_WORD);
     if (isLinux || isMac) {
       checkSelection(frame.contentWindow.document, "SELECT_WORD", "ttestselection2");
     } else if (isWindows) {
       checkSelection(frame.contentWindow.document, "SELECT_WORD", "ttestselection2 ");
     }