diff --git a/racket-webview-qt.rkt b/racket-webview-qt.rkt
index 4c43b23..d3679a3 100644
--- a/racket-webview-qt.rkt
+++ b/racket-webview-qt.rkt
@@ -844,7 +844,7 @@
     (dbg-webview "Stopping event processing thread (kill-thread)")
     (stop-event-processing)
     (dbg-webview "Finalizer done")
-    (set finalizer-executed #t)
+    (set! finalizer-executed #t)
     )
   )