diff --git a/src/Symfony/Component/Stopwatch/Stopwatch.php b/src/Symfony/Component/Stopwatch/Stopwatch.php
index 19e59bec501f5..9a3fe56d86e78 100644
--- a/src/Symfony/Component/Stopwatch/Stopwatch.php
+++ b/src/Symfony/Component/Stopwatch/Stopwatch.php
@@ -81,7 +81,7 @@ public function openSection(string $id = null)
      *
      * @throws \LogicException When there's no started section to be stopped
      */
-    public function stopSection(?string $id)
+    public function stopSection(string $id)
     {
         $this->stop('__section__');