diff --git a/src/js/config.js b/src/js/config.js
index 1db168c0b..6e90de776 100644
--- a/src/js/config.js
+++ b/src/js/config.js
@@ -916,7 +916,8 @@ export function setHighlightMode(mode, nosave) {
     (config.funbox === "nospace" ||
       config.funbox === "read_ahead" ||
       config.funbox === "read_ahead_easy" ||
-      config.funbox === "read_ahead_hard")
+      config.funbox === "read_ahead_hard" ||
+      config.funbox === "tts")
   ) {
     Notifications.add("Can't use word highlight with this funbox", 0);
     return;
diff --git a/src/js/test/funbox.js b/src/js/test/funbox.js
index 0685e6f0c..470bcb5cf 100644
--- a/src/js/test/funbox.js
+++ b/src/js/test/funbox.js
@@ -167,6 +167,7 @@ export async function activate(funbox) {
         UpdateConfig.setKeymapMode
       );
       UpdateConfig.setKeymapMode("off");
+      UpdateConfig.setHighlightMode("letter");
       Settings.groups.keymapMode.updateButton();
       TestLogic.restart();
     } else if (funbox === "layoutfluid") {