1 files changed, 1 insertions, 1 deletions
diff --git a/toolkit/mozapps/extensions/test/browser/browser_webapi_theme.js b/toolkit/mozapps/extensions/test/browser/browser_webapi_theme.js
index dd1df90907..f271cbd9e3 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_webapi_theme.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_webapi_theme.js
@@ -13,7 +13,7 @@ add_task(async function test_theme_install() {
 
   await BrowserTestUtils.withNewTab(TESTPAGE, async browser => {
     let updates = [];
-    function observer(subject, topic, data) {
+    function observer(subject) {
       updates.push(JSON.stringify(subject.wrappedJSObject));
     }
     Services.obs.addObserver(observer, "lightweight-theme-styling-update");