diff --git a/lib/public/AppFramework/Http/Response.php b/lib/public/AppFramework/Http/Response.php
index 046faa9f2053c..5258a1024703f 100644
--- a/lib/public/AppFramework/Http/Response.php
+++ b/lib/public/AppFramework/Http/Response.php
@@ -11,6 +11,7 @@
 use OCP\AppFramework\Utility\ITimeFactory;
 use OCP\IConfig;
 use OCP\IRequest;
+use OCP\IUserSession;
 use Psr\Log\LoggerInterface;
 
 /**
@@ -246,6 +247,11 @@ public function getHeaders() {
 			$mergeWith['ETag'] = '"' . $this->ETag . '"';
 		}
 
+		$userSession = \OC::$server->get(IUserSession::class);
+		if ($user = $userSession->getUser()) {
+			$mergeWith['X-User-Id'] = $user->getUID();
+		}
+
 		return array_merge($mergeWith, $this->headers);
 	}