diff --git a/background.js b/background.js
index 1f7cdd70..9a077515 100644
--- a/background.js
+++ b/background.js
@@ -100,7 +100,7 @@ function registerFirefoxContentScript(options) {
         js: options.js,
         css: options.css,
         matches: options.matches
-    }).then(() => void (contentScriptRegistrations[options.id] = registration));
+    }).then((registration) => void (contentScriptRegistrations[options.id] = registration));
 }
 
 //gets the sponsor times from memory