diff --git a/core/lib/Drupal/Core/StackMiddleware/ServerTiming.php b/core/lib/Drupal/Core/StackMiddleware/ServerTiming.php
index dea36ed427..03bcba8372 100644
--- a/core/lib/Drupal/Core/StackMiddleware/ServerTiming.php
+++ b/core/lib/Drupal/Core/StackMiddleware/ServerTiming.php
@@ -34,8 +34,10 @@ public function __construct(HttpKernelInterface $http_kernel) {
    */
   public function handle(Request $request, $type = self::MASTER_REQUEST, $catch = TRUE) {
     $response = $this->httpKernel->handle($request, $type, $catch);
-    $duration = round(1000 * (microtime(TRUE) - $request->server->get('REQUEST_TIME_FLOAT')), 2);
-    $response->headers->set('Server-Timing', 'total;desc="Page execution time";dur=' . $duration, FALSE);
+    if ($type == self::MASTER_REQUEST) {
+      $duration = round(1000 * (microtime(TRUE) - $request->server->get('REQUEST_TIME_FLOAT')), 2);
+      $response->headers->set('Server-Timing', 'total;desc="Request execution time";dur=' . $duration, FALSE);
+    }
     return $response;
   }
 
diff --git a/core/tests/Drupal/Tests/Core/StackMiddleware/ServerTimingTest.php b/core/tests/Drupal/Tests/Core/StackMiddleware/ServerTimingTest.php
index 539c9e1b3e..7f9570e64e 100644
--- a/core/tests/Drupal/Tests/Core/StackMiddleware/ServerTimingTest.php
+++ b/core/tests/Drupal/Tests/Core/StackMiddleware/ServerTimingTest.php
@@ -43,7 +43,7 @@ public function testServerTiming() {
 
     $expected_headers = [
       'example;desc="Example";dur=456',
-      'total;desc="Page execution time";dur=123.12',
+      'total;desc="Request execution time";dur=123.12',
     ];
     self::assertSame($expected_headers, $response->headers->get('Server-Timing', NULL, FALSE));
   }