--- a/layout/base/PresShell.cpp
+++ b/layout/base/PresShell.cpp
@@ -7472,17 +7472,22 @@ PresShell::HandleEvent(nsIFrame* aFrame,
     // capturing and retargeting the event because the captured frame will
     // be used instead below. Also keep using the root frame if we're dealing
     // with a window-level mouse exit event since we want to start sending
     // mouse out events at the root EventStateManager.
     if (!captureRetarget && !isWindowLevelMouseExit) {
       nsPoint eventPoint;
       uint32_t flags = 0;
       if (aEvent->mMessage == eTouchStart) {
-        flags |= INPUT_IGNORE_ROOT_SCROLL_FRAME;
+        if (gfxPrefs::APZAllowZooming()) {
+          // Setting this flag will skip the scrollbars on the root frame from
+          // participating in hit-testing, and we only want that to happen on
+          // zoomable platforms (for now).
+          flags |= INPUT_IGNORE_ROOT_SCROLL_FRAME;
+        }
         WidgetTouchEvent* touchEvent = aEvent->AsTouchEvent();
         // if this is a continuing session, ensure that all these events are
         // in the same document by taking the target of the events already in
         // the capture list
         nsCOMPtr<nsIContent> anyTarget;
         if (touchEvent->mTouches.Length() > 1) {
           anyTarget = TouchManager::GetAnyCapturedTouchTarget();
         }