diff --git a/src/corelib/kernel/qcoreapplication.cpp b/src/corelib/kernel/qcoreapplication.cpp
index b6f839d554d..ecafe91b433 100644
--- a/src/corelib/kernel/qcoreapplication.cpp
+++ b/src/corelib/kernel/qcoreapplication.cpp
@@ -1005,6 +1005,17 @@ bool QCoreApplication::notifyInternal(QObject *receiver, QEvent *event)
   do not change the focus widget.
   \endlist
 
+  \b{Future direction:} This function will not be called for objects that live
+  outside the main thread in Qt 6. Applications that need that functionality
+  should find other solutions for their event inspection needs in the meantime.
+  The change may be extended to the main thread, causing this function to be
+  deprecated.
+
+  \warning If you override this function, you must ensure all threads that
+  process events stop doing so before your application object begins
+  destruction. This includes threads started by other libraries that you may be
+  using, but does not apply to Qt's own threads.
+
   \sa QObject::event(), installNativeEventFilter()
 */