diff --git a/php/src/Controller/DockerController.php b/php/src/Controller/DockerController.php
index 8fa208b4..e7359c7b 100644
--- a/php/src/Controller/DockerController.php
+++ b/php/src/Controller/DockerController.php
@@ -403,6 +403,7 @@ readonly class DockerController {
             ->withBody(new NonBufferedBody())
             ->withHeader('Content-Type', 'text/html; charset=utf-8')
             ->withHeader('X-Accel-Buffering', 'no')
+            ->withHeader('Content-Length', '-1')
             ->withHeader('Cache-Control', 'no-cache');
             
         // Text written into this body is immediately sent to the client, without waiting for later content.