diff --git a/app/worker.ts b/app/worker.ts
index 678329d..22da966 100644
--- a/app/worker.ts
+++ b/app/worker.ts
@@ -182,6 +182,9 @@ export default function start(self: ServiceWorkerGlobalScope) {
         {
           method: "POST",
           body: JSON.stringify(subscription),
+          headers: {
+            "Content-Type": "application/json",
+          },
         }
       )
 
@@ -203,6 +206,9 @@ export default function start(self: ServiceWorkerGlobalScope) {
     return fetch(`${process.env.BASE_URL}/api/subscription/${id}`, {
       method: "PUT",
       body: JSON.stringify(subscription),
+      headers: {
+        "Content-Type": "application/json",
+      },
     })
   }
 }