diff --git a/src/Symfony/Component/Messenger/Tests/Transport/Serialization/PhpSerializerTest.php b/src/Symfony/Component/Messenger/Tests/Transport/Serialization/PhpSerializerTest.php
index 5076577b02..96f4503c2e 100644
--- a/src/Symfony/Component/Messenger/Tests/Transport/Serialization/PhpSerializerTest.php
+++ b/src/Symfony/Component/Messenger/Tests/Transport/Serialization/PhpSerializerTest.php
@@ -76,6 +76,17 @@ class PhpSerializerTest extends TestCase
         $encoded = $serializer->encode($envelope);
         $this->assertStringNotContainsString('DummyPhpSerializerNonSendableStamp', $encoded['body']);
     }
+
+    public function testNonUtf8IsBase64Encoded()
+    {
+        $serializer = new PhpSerializer();
+
+        $envelope = new Envelope(new DummyMessage("\xE9"));
+
+        $encoded = $serializer->encode($envelope);
+        $this->assertTrue((bool) preg_match('//u', $encoded['body']), 'Encodes non-UTF8 payloads');
+        $this->assertEquals($envelope, $serializer->decode($encoded));
+    }
 }
 
 class DummyPhpSerializerNonSendableStamp implements NonSendableStampInterface
diff --git a/src/Symfony/Component/Messenger/Transport/Serialization/PhpSerializer.php b/src/Symfony/Component/Messenger/Transport/Serialization/PhpSerializer.php
index e166812598..42e0056022 100644
--- a/src/Symfony/Component/Messenger/Transport/Serialization/PhpSerializer.php
+++ b/src/Symfony/Component/Messenger/Transport/Serialization/PhpSerializer.php
@@ -29,6 +29,10 @@ class PhpSerializer implements SerializerInterface
             throw new MessageDecodingFailedException('Encoded envelope should have at least a "body".');
         }
 
+        if (false === strpos($encodedEnvelope['body'], '}', -1)) {
+            $encodedEnvelope['body'] = base64_decode($encodedEnvelope['body']);
+        }
+
         $serializeEnvelope = stripslashes($encodedEnvelope['body']);
 
         return $this->safelyUnserialize($serializeEnvelope);
@@ -43,6 +47,10 @@ class PhpSerializer implements SerializerInterface
 
         $body = addslashes(serialize($envelope));
 
+        if (!preg_match('//u', $body)) {
+            $body = base64_encode($body);
+        }
+
         return [
             'body' => $body,
         ];