diff --git a/src/Symfony/Component/Lock/Lock.php b/src/Symfony/Component/Lock/Lock.php
index f7da528d1c..f8302729b0 100644
--- a/src/Symfony/Component/Lock/Lock.php
+++ b/src/Symfony/Component/Lock/Lock.php
@@ -67,7 +67,7 @@ final class Lock implements LockInterface, LoggerAwareInterface
     /**
      * {@inheritdoc}
      */
-    public function acquire($blocking = false): ?bool
+    public function acquire($blocking = false): bool
     {
         try {
             if ($blocking) {