diff -ur '--exclude=*.decls' '--exclude=*.h' '--exclude=*.orig' '--exclude=tcl[TN]*.c' tcl.old/generic/tclEvent.c tcl.new/generic/tclEvent.c
--- tcl.old/generic/tclEvent.c	2020-12-11 18:46:22.000000000 +0100
+++ tcl.new/generic/tclEvent.c	2021-03-15 18:50:02.000000000 +0100
@@ -1510,7 +1510,7 @@
 	}
 	switch ((enum updateOptions) optionIndex) {
 	case OPT_IDLETASKS:
-	    flags = TCL_WINDOW_EVENTS|TCL_IDLE_EVENTS|TCL_DONT_WAIT;
+	    flags = TCL_IDLE_EVENTS|TCL_DONT_WAIT;
 	    break;
 	default:
 	    Tcl_Panic("Tcl_UpdateObjCmd: bad option index to UpdateOptions");
