diff --git a/src/core/api.js b/src/core/api.js
index a366ad09..cf5b51a5 100644
--- a/src/core/api.js
+++ b/src/core/api.js
@@ -196,10 +196,10 @@ export function runAPI(express, app, gitCommit, gitBranch, __dirname) {
             return res.sendStatus(404);
         }
 
-        streamInfo.headers = {
-            ...streamInfo.headers,
-            ...req.headers
-        };
+        streamInfo.headers = new Map([
+            streamInfo.headers || {},
+            req.headers
+        ]);
 
         return stream(res, { type: 'internal', ...streamInfo });
     })
diff --git a/src/modules/stream/manage.js b/src/modules/stream/manage.js
index 06c73a6b..af041a67 100644
--- a/src/modules/stream/manage.js
+++ b/src/modules/stream/manage.js
@@ -87,10 +87,15 @@ export function createInternalStream(url, obj = {}) {
         setMaxListeners(Infinity, controller.signal);
     }
 
+    let headers;
+    if (obj.headers) {
+        headers = new Map(Object.entries(obj.headers));
+    }
+
     internalStreamCache[streamID] = {
         url,
         service: obj.service,
-        headers: obj.headers,
+        headers,
         controller,
         dispatcher
     };