diff --git i/src/Symfony/Component/Messenger/Tests/Transport/Serialization/PhpSerializerTest.php w/src/Symfony/Component/Messenger/Tests/Transport/Serialization/PhpSerializerTest.php
index c83606a59f..6091879999 100644
--- i/src/Symfony/Component/Messenger/Tests/Transport/Serialization/PhpSerializerTest.php
+++ w/src/Symfony/Component/Messenger/Tests/Transport/Serialization/PhpSerializerTest.php
@@ -77,6 +77,17 @@ class PhpSerializerTest extends TestCase
         ]);
     }
 
+    public function testDecodingFailsWithBadData()
+    {
+        $this->expectException(MessageDecodingFailedException::class);
+
+        $serializer = $this->createPhpSerializer();
+
+        $serializer->decode([
+            'body' => 'O:8:"DateTime":0:{}',
+        ]);
+    }
+
     public function testEncodedSkipsNonEncodeableStamps()
     {
         $serializer = $this->createPhpSerializer();