diff --git a/devtools/startup/DevToolsStartup.sys.mjs b/devtools/startup/DevToolsStartup.sys.mjs
index 0c9db6cb85c491a9f0fc216071afc66e553dcd51..25648d72f45ce016e3a498cab5a6f24e37c35296 100644
--- a/devtools/startup/DevToolsStartup.sys.mjs
+++ b/devtools/startup/DevToolsStartup.sys.mjs
@@ -806,6 +806,7 @@ DevToolsStartup.prototype = {
     // account (see bug 832984).
     const mainKeyset = doc.getElementById("mainKeyset");
     mainKeyset.parentNode.insertBefore(keyset, mainKeyset);
+    window.dispatchEvent(new window.Event("zen-devtools-keyset-added"));
   },
 
   /**