--- a/widget/gtk/nsWindow.cpp
+++ b/widget/gtk/nsWindow.cpp
@@ -3496,21 +3496,51 @@ nsWindow::OnDragDataReceivedEvent(GtkWid
     LOGDRAG(("nsWindow::OnDragDataReceived(%p)\n", (void*)this));
 
     RefPtr<nsDragService> dragService = nsDragService::GetInstance();
     dragService->
         TargetDataReceived(aWidget, aDragContext, aX, aY,
                            aSelectionData, aInfo, aTime);
 }
 
+nsWindow*
+nsWindow::GetTransientForWindowIfPopup()
+{
+    if (mWindowType != eWindowType_popup) {
+        return nullptr;
+    }
+    GtkWindow* toplevel = gtk_window_get_transient_for(GTK_WINDOW(mShell));
+    if (toplevel) {
+        return get_window_for_gtk_widget(GTK_WIDGET(toplevel));
+    }
+    return nullptr;
+}
+
+bool
+nsWindow::IsHandlingTouchSequence(GdkEventSequence* aSequence)
+{
+    return mHandleTouchEvent && mTouches.Contains(aSequence);
+}
+
 #if GTK_CHECK_VERSION(3,4,0)
 gboolean
 nsWindow::OnTouchEvent(GdkEventTouch* aEvent)
 {
     if (!mHandleTouchEvent) {
+        // If a popup window was spawned (e.g. as the result of a long-press)
+        // and touch events got diverted to that window within a touch sequence,
+        // ensure the touch event gets sent to the original window instead. We
+        // keep the checks here very conservative so that we only redirect
+        // events in this specific scenario.
+        nsWindow* targetWindow = GetTransientForWindowIfPopup();
+        if (targetWindow &&
+            targetWindow->IsHandlingTouchSequence(aEvent->sequence)) {
+            return targetWindow->OnTouchEvent(aEvent);
+        }
+
         return FALSE;
     }
 
     EventMessage msg;
     switch (aEvent->type) {
     case GDK_TOUCH_BEGIN:
         msg = eTouchStart;
         break;
@@ -4838,22 +4868,26 @@ nsWindow::GrabPointer(guint32 aTime)
 
     if (!mIsX11Display) {
         // Don't to the grab on Wayland as it causes a regression
         // from Bug 1377084.
         return;
     }
 
     gint retval;
+    // Note that we need GDK_TOUCH_MASK below to work around a GDK/X11 bug that
+    // causes touch events that would normally be received by this client on
+    // other windows to be discarded during the grab.
     retval = gdk_pointer_grab(mGdkWindow, TRUE,
                               (GdkEventMask)(GDK_BUTTON_PRESS_MASK |
                                              GDK_BUTTON_RELEASE_MASK |
                                              GDK_ENTER_NOTIFY_MASK |
                                              GDK_LEAVE_NOTIFY_MASK |
-                                             GDK_POINTER_MOTION_MASK),
+                                             GDK_POINTER_MOTION_MASK |
+                                             GDK_TOUCH_MASK),
                               (GdkWindow *)nullptr, nullptr, aTime);
 
     if (retval == GDK_GRAB_NOT_VIEWABLE) {
         LOG(("GrabPointer: window not viewable; will retry\n"));
         mRetryPointerGrab = true;
     } else if (retval != GDK_GRAB_SUCCESS) {
         LOG(("GrabPointer: pointer grab failed: %i\n", retval));
         // A failed grab indicates that another app has grabbed the pointer.

--- a/widget/gtk/nsWindow.h
+++ b/widget/gtk/nsWindow.h
@@ -491,16 +491,19 @@ private:
                                    GdkWindow** aWindow, gint* aButton,
                                    gint* aRootX, gint* aRootY);
     void               ClearCachedResources();
     nsIWidgetListener* GetListener();
     bool               IsComposited() const;
 
     void               UpdateClientOffsetForCSDWindow();
 
+    nsWindow*          GetTransientForWindowIfPopup();
+    bool               IsHandlingTouchSequence(GdkEventSequence* aSequence);
+
 #ifdef MOZ_X11
     typedef enum { GTK_WIDGET_COMPOSIDED_DEFAULT = 0,
                    GTK_WIDGET_COMPOSIDED_DISABLED = 1,
                    GTK_WIDGET_COMPOSIDED_ENABLED = 2
     } WindowComposeRequest;
 
     void                SetCompositorHint(WindowComposeRequest aState);
 #endif