diff --git a/script/serviceWorker.js b/script/serviceWorker.js
index 98fe5cd..d45a530 100644
--- a/script/serviceWorker.js
+++ b/script/serviceWorker.js
@@ -226,6 +226,9 @@ async function refreshTokens(event) {
 		method: 'POST',
 		signal: controller.signal,
 		credentials: 'include',
+		headers: {
+			'Content-Type': 'application/json',
+		},
 	});
 	event.waitUntil(refreshResponse);