From 41a998022602483eda9a65ee8a5c5620fd7c0d61 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kamil=20Og=C3=B3rek?= <kamil.ogorek@gmail.com>
Date: Wed, 15 Sep 2021 19:46:48 +0200
Subject: [PATCH] fix: Envelope header is required

---
 packages/browser/src/transports/base.ts | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/packages/browser/src/transports/base.ts b/packages/browser/src/transports/base.ts
index 98e911b9427d..876a9c009fcc 100644
--- a/packages/browser/src/transports/base.ts
+++ b/packages/browser/src/transports/base.ts
@@ -107,6 +107,8 @@ export abstract class BaseTransport implements Transport {
     logger.log(`Flushing outcomes:\n${JSON.stringify(outcomes, null, 2)}`);
 
     const url = this._api.getEnvelopeEndpointWithUrlEncodedAuth();
+    // Envelope header is required to be at least an empty object
+    const envelopeHeader = JSON.stringify({});
     const itemHeaders = JSON.stringify({
       type: 'client_report',
     });
@@ -121,7 +123,7 @@ export abstract class BaseTransport implements Transport {
         };
       }),
     });
-    const envelope = `${itemHeaders}\n${item}`;
+    const envelope = `${envelopeHeader}\n${itemHeaders}\n${item}`;
 
     navigator.sendBeacon(url, envelope);
   }