diff --git a/packages/start-server-core/src/server-functions-handler.ts b/packages/start-server-core/src/server-functions-handler.ts
index 8cd98cf30be..69e0dc19bc4 100644
--- a/packages/start-server-core/src/server-functions-handler.ts
+++ b/packages/start-server-core/src/server-functions-handler.ts
@@ -232,10 +232,11 @@ export const handleServerAction = async ({
         }
 
         // not done yet, we need to stream
+        const encoder = new TextEncoder()
         const stream = new ReadableStream({
           start(controller) {
             callbacks.onParse = (value) =>
-              controller.enqueue(JSON.stringify(value) + '\n')
+              controller.enqueue(encoder.encode(JSON.stringify(value) + '\n'))
             callbacks.onDone = () => {
               try {
                 controller.close()