diff --git a/micromamba.el b/micromamba.el
index 333d065..5246b64 100644
--- a/micromamba.el
+++ b/micromamba.el
@@ -321,8 +321,9 @@ buffer."
   (if micromamba-env-autoactivate-mode ;; already on, now switching off
     (add-to-list 'window-selection-change-functions
                  #'micromamba--switch-buffer-auto-activate)
-    (delete #'micromamba--switch-buffer-auto-activate
-            window-selection-change-functions)))
+    (setq window-selection-change-functions
+          (delete #'micromamba--switch-buffer-auto-activate
+                  window-selection-change-functions))))
 
 (provide 'micromamba)
 ;;; micromamba.el ends here