diff --git a/.github/build-packages.php b/.github/build-packages.php
index 95ff7fc1a8..eb5cc6757e 100644
--- a/.github/build-packages.php
+++ b/.github/build-packages.php
@@ -54,7 +54,6 @@ foreach ($dirs as $k => $dir) {
         echo "Missing \"version\" in composer.json.\n";
         exit(1);
     }
-    $package->version = str_replace('-dev', '.x-dev', $package->version);
     $package->dist['type'] = 'tar';
     $package->dist['url'] = 'file://'.str_replace(DIRECTORY_SEPARATOR, '/', dirname(__DIR__))."/$dir/package.tar";
 
diff --git a/.travis.yml b/.travis.yml
index be3b224e15..fe993abbd2 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -209,7 +209,7 @@ install:
           git fetch --depth=2 origin refs/pull/$SYMFONY_PHPUNIT_BRIDGE_PR/head
           git rm -rq src/Symfony/Bridge/PhpUnit
           git checkout -q FETCH_HEAD -- src/Symfony/Bridge/PhpUnit
-          export SYMFONY_VERSION=$(cat src/Symfony/Bridge/PhpUnit/composer.json | grep '^ *"version": *"[1-9]' | grep -o '[0-9.]*')
+          export SYMFONY_VERSION=$(cat src/Symfony/Bridge/PhpUnit/composer.json | grep '^ *"version": *"[1-9]' | grep -o '[0-9.]*[0-9]')
           sed -i 's/"symfony\/phpunit-bridge": ".*"/"symfony\/phpunit-bridge": "'$SYMFONY_VERSION'.x@dev"/' composer.json
           rm -rf .phpunit
       fi
@@ -243,7 +243,7 @@ install:
           git checkout -m FETCH_HEAD &&
           export COMPONENTS=$(find src/Symfony -mindepth 2 -type f -name phpunit.xml.dist -printf '%h\n' | sort)
       else
-          export SYMFONY_VERSION=$(cat composer.json | grep '^ *"version". *"[1-9]' | grep -o '[0-9.]*')
+          export SYMFONY_VERSION=$(cat composer.json | grep '^ *"version". *"[1-9]' | grep -o '[0-9.]*[0-9]')
       fi
 
     - |
diff --git a/src/Symfony/Bridge/Doctrine/composer.json b/src/Symfony/Bridge/Doctrine/composer.json
index 3f13dcaf8e..76de900c61 100644
--- a/src/Symfony/Bridge/Doctrine/composer.json
+++ b/src/Symfony/Bridge/Doctrine/composer.json
@@ -76,5 +76,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Bridge/Monolog/composer.json b/src/Symfony/Bridge/Monolog/composer.json
index 6017fda31d..1c7ad3c8ee 100644
--- a/src/Symfony/Bridge/Monolog/composer.json
+++ b/src/Symfony/Bridge/Monolog/composer.json
@@ -45,5 +45,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Bridge/PhpUnit/composer.json b/src/Symfony/Bridge/PhpUnit/composer.json
index e57b524aa8..f6b9fbf9b0 100644
--- a/src/Symfony/Bridge/PhpUnit/composer.json
+++ b/src/Symfony/Bridge/PhpUnit/composer.json
@@ -46,5 +46,5 @@
             "url": "https://github.com/sebastianbergmann/phpunit"
         }
     },
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Bridge/ProxyManager/composer.json b/src/Symfony/Bridge/ProxyManager/composer.json
index 42b1e5354c..f666ec7b1e 100644
--- a/src/Symfony/Bridge/ProxyManager/composer.json
+++ b/src/Symfony/Bridge/ProxyManager/composer.json
@@ -33,5 +33,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Bridge/Twig/composer.json b/src/Symfony/Bridge/Twig/composer.json
index c0e1e8d518..247bd68889 100644
--- a/src/Symfony/Bridge/Twig/composer.json
+++ b/src/Symfony/Bridge/Twig/composer.json
@@ -78,5 +78,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Bundle/DebugBundle/composer.json b/src/Symfony/Bundle/DebugBundle/composer.json
index ee2a3883f9..f6cafcd81a 100644
--- a/src/Symfony/Bundle/DebugBundle/composer.json
+++ b/src/Symfony/Bundle/DebugBundle/composer.json
@@ -42,5 +42,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Bundle/FrameworkBundle/composer.json b/src/Symfony/Bundle/FrameworkBundle/composer.json
index b67fbdc776..f425e676a4 100644
--- a/src/Symfony/Bundle/FrameworkBundle/composer.json
+++ b/src/Symfony/Bundle/FrameworkBundle/composer.json
@@ -109,5 +109,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Bundle/SecurityBundle/composer.json b/src/Symfony/Bundle/SecurityBundle/composer.json
index 60e4f640ba..13bc721a33 100644
--- a/src/Symfony/Bundle/SecurityBundle/composer.json
+++ b/src/Symfony/Bundle/SecurityBundle/composer.json
@@ -61,5 +61,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Bundle/TwigBundle/composer.json b/src/Symfony/Bundle/TwigBundle/composer.json
index bfa079a6df..d7fcb768af 100644
--- a/src/Symfony/Bundle/TwigBundle/composer.json
+++ b/src/Symfony/Bundle/TwigBundle/composer.json
@@ -51,5 +51,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Bundle/WebProfilerBundle/composer.json b/src/Symfony/Bundle/WebProfilerBundle/composer.json
index 7f578d3355..8de6cfad55 100644
--- a/src/Symfony/Bundle/WebProfilerBundle/composer.json
+++ b/src/Symfony/Bundle/WebProfilerBundle/composer.json
@@ -41,5 +41,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Asset/composer.json b/src/Symfony/Component/Asset/composer.json
index 8d2694e3ee..081597de94 100644
--- a/src/Symfony/Component/Asset/composer.json
+++ b/src/Symfony/Component/Asset/composer.json
@@ -33,5 +33,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/BrowserKit/composer.json b/src/Symfony/Component/BrowserKit/composer.json
index 6a91e1b13f..c71e791b2a 100644
--- a/src/Symfony/Component/BrowserKit/composer.json
+++ b/src/Symfony/Component/BrowserKit/composer.json
@@ -35,5 +35,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Cache/composer.json b/src/Symfony/Component/Cache/composer.json
index fc143ffe52..bd96d9b2b4 100644
--- a/src/Symfony/Component/Cache/composer.json
+++ b/src/Symfony/Component/Cache/composer.json
@@ -52,5 +52,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Config/composer.json b/src/Symfony/Component/Config/composer.json
index 140bdd15d6..1baddd3675 100644
--- a/src/Symfony/Component/Config/composer.json
+++ b/src/Symfony/Component/Config/composer.json
@@ -42,5 +42,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Console/composer.json b/src/Symfony/Component/Console/composer.json
index e99f6a51b7..32e82f4b0e 100644
--- a/src/Symfony/Component/Console/composer.json
+++ b/src/Symfony/Component/Console/composer.json
@@ -55,5 +55,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/CssSelector/composer.json b/src/Symfony/Component/CssSelector/composer.json
index f1bb610467..65e03061ad 100644
--- a/src/Symfony/Component/CssSelector/composer.json
+++ b/src/Symfony/Component/CssSelector/composer.json
@@ -29,5 +29,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/DependencyInjection/composer.json b/src/Symfony/Component/DependencyInjection/composer.json
index e3f5740c10..149f4fc728 100644
--- a/src/Symfony/Component/DependencyInjection/composer.json
+++ b/src/Symfony/Component/DependencyInjection/composer.json
@@ -51,5 +51,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/DomCrawler/composer.json b/src/Symfony/Component/DomCrawler/composer.json
index d33e0bdc26..80ae7c99dd 100644
--- a/src/Symfony/Component/DomCrawler/composer.json
+++ b/src/Symfony/Component/DomCrawler/composer.json
@@ -38,5 +38,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Dotenv/composer.json b/src/Symfony/Component/Dotenv/composer.json
index e005d9ac87..ea70fcf5bb 100644
--- a/src/Symfony/Component/Dotenv/composer.json
+++ b/src/Symfony/Component/Dotenv/composer.json
@@ -29,5 +29,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/ErrorHandler/composer.json b/src/Symfony/Component/ErrorHandler/composer.json
index e1fa821cb8..8af96e4b42 100644
--- a/src/Symfony/Component/ErrorHandler/composer.json
+++ b/src/Symfony/Component/ErrorHandler/composer.json
@@ -33,5 +33,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/EventDispatcher/composer.json b/src/Symfony/Component/EventDispatcher/composer.json
index 01f1425180..d50d6dad0c 100644
--- a/src/Symfony/Component/EventDispatcher/composer.json
+++ b/src/Symfony/Component/EventDispatcher/composer.json
@@ -49,5 +49,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/ExpressionLanguage/composer.json b/src/Symfony/Component/ExpressionLanguage/composer.json
index 6dbd810f2c..30ca9cd9da 100644
--- a/src/Symfony/Component/ExpressionLanguage/composer.json
+++ b/src/Symfony/Component/ExpressionLanguage/composer.json
@@ -28,5 +28,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Filesystem/composer.json b/src/Symfony/Component/Filesystem/composer.json
index 8de6c550c9..c33d7440d2 100644
--- a/src/Symfony/Component/Filesystem/composer.json
+++ b/src/Symfony/Component/Filesystem/composer.json
@@ -26,5 +26,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Finder/composer.json b/src/Symfony/Component/Finder/composer.json
index 2ef83e810a..31d7311d87 100644
--- a/src/Symfony/Component/Finder/composer.json
+++ b/src/Symfony/Component/Finder/composer.json
@@ -25,5 +25,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Form/composer.json b/src/Symfony/Component/Form/composer.json
index c8e0152d46..163dcc926c 100644
--- a/src/Symfony/Component/Form/composer.json
+++ b/src/Symfony/Component/Form/composer.json
@@ -65,5 +65,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/HttpClient/composer.json b/src/Symfony/Component/HttpClient/composer.json
index bde91ec156..2032022be2 100644
--- a/src/Symfony/Component/HttpClient/composer.json
+++ b/src/Symfony/Component/HttpClient/composer.json
@@ -47,5 +47,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/HttpFoundation/composer.json b/src/Symfony/Component/HttpFoundation/composer.json
index f59d52f2f8..e60573d4e0 100644
--- a/src/Symfony/Component/HttpFoundation/composer.json
+++ b/src/Symfony/Component/HttpFoundation/composer.json
@@ -37,5 +37,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/HttpKernel/composer.json b/src/Symfony/Component/HttpKernel/composer.json
index 37cb54ae42..74d99ac5c8 100644
--- a/src/Symfony/Component/HttpKernel/composer.json
+++ b/src/Symfony/Component/HttpKernel/composer.json
@@ -76,5 +76,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Inflector/composer.json b/src/Symfony/Component/Inflector/composer.json
index 8cb0e496b8..3d451614aa 100644
--- a/src/Symfony/Component/Inflector/composer.json
+++ b/src/Symfony/Component/Inflector/composer.json
@@ -34,5 +34,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Intl/composer.json b/src/Symfony/Component/Intl/composer.json
index 3bcac6999e..f39ab4619b 100644
--- a/src/Symfony/Component/Intl/composer.json
+++ b/src/Symfony/Component/Intl/composer.json
@@ -42,5 +42,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Ldap/composer.json b/src/Symfony/Component/Ldap/composer.json
index e201e9d43a..db76ed0cea 100644
--- a/src/Symfony/Component/Ldap/composer.json
+++ b/src/Symfony/Component/Ldap/composer.json
@@ -35,5 +35,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Lock/composer.json b/src/Symfony/Component/Lock/composer.json
index 963a58a1ff..0e01735ee0 100644
--- a/src/Symfony/Component/Lock/composer.json
+++ b/src/Symfony/Component/Lock/composer.json
@@ -35,5 +35,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Mailer/Bridge/Amazon/composer.json b/src/Symfony/Component/Mailer/Bridge/Amazon/composer.json
index 425bd8d04c..e109d0b9ef 100644
--- a/src/Symfony/Component/Mailer/Bridge/Amazon/composer.json
+++ b/src/Symfony/Component/Mailer/Bridge/Amazon/composer.json
@@ -31,5 +31,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Mailer/Bridge/Google/composer.json b/src/Symfony/Component/Mailer/Bridge/Google/composer.json
index cb4f94c0cf..6d4a3a7046 100644
--- a/src/Symfony/Component/Mailer/Bridge/Google/composer.json
+++ b/src/Symfony/Component/Mailer/Bridge/Google/composer.json
@@ -29,5 +29,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Mailer/Bridge/Mailchimp/composer.json b/src/Symfony/Component/Mailer/Bridge/Mailchimp/composer.json
index 61d8ffc9be..019bf34015 100644
--- a/src/Symfony/Component/Mailer/Bridge/Mailchimp/composer.json
+++ b/src/Symfony/Component/Mailer/Bridge/Mailchimp/composer.json
@@ -29,5 +29,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Mailer/Bridge/Mailgun/composer.json b/src/Symfony/Component/Mailer/Bridge/Mailgun/composer.json
index 392de08f0f..605afb9c49 100644
--- a/src/Symfony/Component/Mailer/Bridge/Mailgun/composer.json
+++ b/src/Symfony/Component/Mailer/Bridge/Mailgun/composer.json
@@ -29,5 +29,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Mailer/Bridge/Postmark/composer.json b/src/Symfony/Component/Mailer/Bridge/Postmark/composer.json
index 0170937414..a9b465b04c 100644
--- a/src/Symfony/Component/Mailer/Bridge/Postmark/composer.json
+++ b/src/Symfony/Component/Mailer/Bridge/Postmark/composer.json
@@ -29,5 +29,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Mailer/Bridge/Sendgrid/composer.json b/src/Symfony/Component/Mailer/Bridge/Sendgrid/composer.json
index 72d4725fbf..946ce1f1ee 100644
--- a/src/Symfony/Component/Mailer/Bridge/Sendgrid/composer.json
+++ b/src/Symfony/Component/Mailer/Bridge/Sendgrid/composer.json
@@ -29,5 +29,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Mailer/composer.json b/src/Symfony/Component/Mailer/composer.json
index a601597891..313348f6d3 100644
--- a/src/Symfony/Component/Mailer/composer.json
+++ b/src/Symfony/Component/Mailer/composer.json
@@ -44,5 +44,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Messenger/Bridge/AmazonSqs/composer.json b/src/Symfony/Component/Messenger/Bridge/AmazonSqs/composer.json
index eaea066f00..ce71c624dd 100644
--- a/src/Symfony/Component/Messenger/Bridge/AmazonSqs/composer.json
+++ b/src/Symfony/Component/Messenger/Bridge/AmazonSqs/composer.json
@@ -33,5 +33,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Messenger/Bridge/Amqp/composer.json b/src/Symfony/Component/Messenger/Bridge/Amqp/composer.json
index 3f63e7ab9a..4518343a66 100644
--- a/src/Symfony/Component/Messenger/Bridge/Amqp/composer.json
+++ b/src/Symfony/Component/Messenger/Bridge/Amqp/composer.json
@@ -32,5 +32,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Messenger/Bridge/Doctrine/composer.json b/src/Symfony/Component/Messenger/Bridge/Doctrine/composer.json
index 73ca76fbf7..0016860549 100644
--- a/src/Symfony/Component/Messenger/Bridge/Doctrine/composer.json
+++ b/src/Symfony/Component/Messenger/Bridge/Doctrine/composer.json
@@ -36,5 +36,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Messenger/Bridge/Redis/composer.json b/src/Symfony/Component/Messenger/Bridge/Redis/composer.json
index f224a345da..8b53ce1004 100644
--- a/src/Symfony/Component/Messenger/Bridge/Redis/composer.json
+++ b/src/Symfony/Component/Messenger/Bridge/Redis/composer.json
@@ -30,5 +30,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Messenger/composer.json b/src/Symfony/Component/Messenger/composer.json
index b4daff6d13..78cccb0b1e 100644
--- a/src/Symfony/Component/Messenger/composer.json
+++ b/src/Symfony/Component/Messenger/composer.json
@@ -52,5 +52,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Mime/RawMessage.php b/src/Symfony/Component/Mime/RawMessage.php
index 79a27e9fcc..66788d8ad5 100644
--- a/src/Symfony/Component/Mime/RawMessage.php
+++ b/src/Symfony/Component/Mime/RawMessage.php
@@ -78,7 +78,7 @@ class RawMessage implements \Serializable
 
     public function __serialize(): array
     {
-        return [$this->message];
+        return [$this->toString()];
     }
 
     public function __unserialize(array $data): void
diff --git a/src/Symfony/Component/Mime/Tests/RawMessageTest.php b/src/Symfony/Component/Mime/Tests/RawMessageTest.php
index 5d1588bff0..26e7605bab 100644
--- a/src/Symfony/Component/Mime/Tests/RawMessageTest.php
+++ b/src/Symfony/Component/Mime/Tests/RawMessageTest.php
@@ -32,4 +32,18 @@ class RawMessageTest extends TestCase
         $this->assertEquals('some string', $message->toString());
         $this->assertEquals('some string', implode('', iterator_to_array($message->toIterable())));
     }
+
+    public function testSerialization()
+    {
+        $message = new RawMessage('string');
+        $this->assertEquals('string', unserialize(serialize($message))->toString());
+        // calling methods more than once work
+        $this->assertEquals('string', unserialize(serialize($message))->toString());
+
+        $message = new RawMessage(new \ArrayObject(['some', ' ', 'string']));
+        $message = new RawMessage($message->toIterable());
+        $this->assertEquals('some string', unserialize(serialize($message))->toString());
+        // calling methods more than once work
+        $this->assertEquals('some string', unserialize(serialize($message))->toString());
+    }
 }
diff --git a/src/Symfony/Component/Mime/composer.json b/src/Symfony/Component/Mime/composer.json
index bdad742b6e..726a903c42 100644
--- a/src/Symfony/Component/Mime/composer.json
+++ b/src/Symfony/Component/Mime/composer.json
@@ -35,5 +35,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Notifier/Bridge/Firebase/composer.json b/src/Symfony/Component/Notifier/Bridge/Firebase/composer.json
index 4856f25198..1175ad910c 100644
--- a/src/Symfony/Component/Notifier/Bridge/Firebase/composer.json
+++ b/src/Symfony/Component/Notifier/Bridge/Firebase/composer.json
@@ -27,5 +27,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Notifier/Bridge/FreeMobile/composer.json b/src/Symfony/Component/Notifier/Bridge/FreeMobile/composer.json
index 75125b5c92..0f51e435bf 100644
--- a/src/Symfony/Component/Notifier/Bridge/FreeMobile/composer.json
+++ b/src/Symfony/Component/Notifier/Bridge/FreeMobile/composer.json
@@ -28,5 +28,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Notifier/Bridge/Mattermost/composer.json b/src/Symfony/Component/Notifier/Bridge/Mattermost/composer.json
index 448e9b5360..333d2b4c04 100644
--- a/src/Symfony/Component/Notifier/Bridge/Mattermost/composer.json
+++ b/src/Symfony/Component/Notifier/Bridge/Mattermost/composer.json
@@ -27,5 +27,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Notifier/Bridge/Nexmo/composer.json b/src/Symfony/Component/Notifier/Bridge/Nexmo/composer.json
index 22992e1929..2e6608c84c 100644
--- a/src/Symfony/Component/Notifier/Bridge/Nexmo/composer.json
+++ b/src/Symfony/Component/Notifier/Bridge/Nexmo/composer.json
@@ -27,5 +27,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Notifier/Bridge/OvhCloud/composer.json b/src/Symfony/Component/Notifier/Bridge/OvhCloud/composer.json
index 3a796a7723..9d0fe0995b 100644
--- a/src/Symfony/Component/Notifier/Bridge/OvhCloud/composer.json
+++ b/src/Symfony/Component/Notifier/Bridge/OvhCloud/composer.json
@@ -27,5 +27,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Notifier/Bridge/RocketChat/composer.json b/src/Symfony/Component/Notifier/Bridge/RocketChat/composer.json
index e4f7b58b31..c22e292418 100644
--- a/src/Symfony/Component/Notifier/Bridge/RocketChat/composer.json
+++ b/src/Symfony/Component/Notifier/Bridge/RocketChat/composer.json
@@ -27,5 +27,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Notifier/Bridge/Sinch/composer.json b/src/Symfony/Component/Notifier/Bridge/Sinch/composer.json
index 5788a5b1f8..b4b6063bc9 100644
--- a/src/Symfony/Component/Notifier/Bridge/Sinch/composer.json
+++ b/src/Symfony/Component/Notifier/Bridge/Sinch/composer.json
@@ -28,5 +28,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Notifier/Bridge/Slack/composer.json b/src/Symfony/Component/Notifier/Bridge/Slack/composer.json
index 1ae20d04f7..0cba7aa82a 100644
--- a/src/Symfony/Component/Notifier/Bridge/Slack/composer.json
+++ b/src/Symfony/Component/Notifier/Bridge/Slack/composer.json
@@ -30,5 +30,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Notifier/Bridge/Telegram/composer.json b/src/Symfony/Component/Notifier/Bridge/Telegram/composer.json
index 36ff35a03e..96ce9fc455 100644
--- a/src/Symfony/Component/Notifier/Bridge/Telegram/composer.json
+++ b/src/Symfony/Component/Notifier/Bridge/Telegram/composer.json
@@ -30,5 +30,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Notifier/Bridge/Twilio/composer.json b/src/Symfony/Component/Notifier/Bridge/Twilio/composer.json
index 52fe09a572..7969f9f1b4 100644
--- a/src/Symfony/Component/Notifier/Bridge/Twilio/composer.json
+++ b/src/Symfony/Component/Notifier/Bridge/Twilio/composer.json
@@ -27,5 +27,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Notifier/composer.json b/src/Symfony/Component/Notifier/composer.json
index 65de5d3c61..d2424ea615 100644
--- a/src/Symfony/Component/Notifier/composer.json
+++ b/src/Symfony/Component/Notifier/composer.json
@@ -29,5 +29,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/OptionsResolver/composer.json b/src/Symfony/Component/OptionsResolver/composer.json
index ca5c6550af..83a0d454e9 100644
--- a/src/Symfony/Component/OptionsResolver/composer.json
+++ b/src/Symfony/Component/OptionsResolver/composer.json
@@ -27,5 +27,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Process/composer.json b/src/Symfony/Component/Process/composer.json
index 2cba59d516..a520313f88 100644
--- a/src/Symfony/Component/Process/composer.json
+++ b/src/Symfony/Component/Process/composer.json
@@ -26,5 +26,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/PropertyAccess/composer.json b/src/Symfony/Component/PropertyAccess/composer.json
index bd84a83d5d..90df821291 100644
--- a/src/Symfony/Component/PropertyAccess/composer.json
+++ b/src/Symfony/Component/PropertyAccess/composer.json
@@ -33,5 +33,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/PropertyInfo/composer.json b/src/Symfony/Component/PropertyInfo/composer.json
index 54bc279a88..358ccaf040 100644
--- a/src/Symfony/Component/PropertyInfo/composer.json
+++ b/src/Symfony/Component/PropertyInfo/composer.json
@@ -52,5 +52,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Routing/composer.json b/src/Symfony/Component/Routing/composer.json
index 65415f5ce6..c2e11bb42c 100644
--- a/src/Symfony/Component/Routing/composer.json
+++ b/src/Symfony/Component/Routing/composer.json
@@ -48,5 +48,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Security/Core/composer.json b/src/Symfony/Component/Security/Core/composer.json
index 83a0be9fca..a54f009336 100644
--- a/src/Symfony/Component/Security/Core/composer.json
+++ b/src/Symfony/Component/Security/Core/composer.json
@@ -51,5 +51,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Security/Csrf/composer.json b/src/Symfony/Component/Security/Csrf/composer.json
index 484fd8ff81..8f50146f26 100644
--- a/src/Symfony/Component/Security/Csrf/composer.json
+++ b/src/Symfony/Component/Security/Csrf/composer.json
@@ -35,5 +35,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Security/Guard/composer.json b/src/Symfony/Component/Security/Guard/composer.json
index cbda524b4b..735ba12c1f 100644
--- a/src/Symfony/Component/Security/Guard/composer.json
+++ b/src/Symfony/Component/Security/Guard/composer.json
@@ -31,5 +31,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Security/Http/composer.json b/src/Symfony/Component/Security/Http/composer.json
index 99b030861c..ed840be2d8 100644
--- a/src/Symfony/Component/Security/Http/composer.json
+++ b/src/Symfony/Component/Security/Http/composer.json
@@ -44,5 +44,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Serializer/composer.json b/src/Symfony/Component/Serializer/composer.json
index ace7954a62..0c6edeef77 100644
--- a/src/Symfony/Component/Serializer/composer.json
+++ b/src/Symfony/Component/Serializer/composer.json
@@ -59,5 +59,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Stopwatch/composer.json b/src/Symfony/Component/Stopwatch/composer.json
index d27ec82134..0751d179a0 100644
--- a/src/Symfony/Component/Stopwatch/composer.json
+++ b/src/Symfony/Component/Stopwatch/composer.json
@@ -26,5 +26,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/String/composer.json b/src/Symfony/Component/String/composer.json
index 2baf279e45..cce4b3df10 100644
--- a/src/Symfony/Component/String/composer.json
+++ b/src/Symfony/Component/String/composer.json
@@ -37,5 +37,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Templating/composer.json b/src/Symfony/Component/Templating/composer.json
index 0dbef8ddad..ea8924fa93 100644
--- a/src/Symfony/Component/Templating/composer.json
+++ b/src/Symfony/Component/Templating/composer.json
@@ -32,5 +32,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Translation/composer.json b/src/Symfony/Component/Translation/composer.json
index 4d02321ebb..05f1e987d0 100644
--- a/src/Symfony/Component/Translation/composer.json
+++ b/src/Symfony/Component/Translation/composer.json
@@ -54,5 +54,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Uid/composer.json b/src/Symfony/Component/Uid/composer.json
index 8a85a46bce..fc03084bb9 100644
--- a/src/Symfony/Component/Uid/composer.json
+++ b/src/Symfony/Component/Uid/composer.json
@@ -30,5 +30,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Validator/composer.json b/src/Symfony/Component/Validator/composer.json
index 931400da01..c2826faf7f 100644
--- a/src/Symfony/Component/Validator/composer.json
+++ b/src/Symfony/Component/Validator/composer.json
@@ -73,5 +73,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/VarDumper/composer.json b/src/Symfony/Component/VarDumper/composer.json
index 1efe21c681..44b83d1cf3 100644
--- a/src/Symfony/Component/VarDumper/composer.json
+++ b/src/Symfony/Component/VarDumper/composer.json
@@ -46,5 +46,5 @@
         "Resources/bin/var-dump-server"
     ],
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/VarExporter/composer.json b/src/Symfony/Component/VarExporter/composer.json
index ca79b7a4b1..041b5f717c 100644
--- a/src/Symfony/Component/VarExporter/composer.json
+++ b/src/Symfony/Component/VarExporter/composer.json
@@ -29,5 +29,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/WebLink/composer.json b/src/Symfony/Component/WebLink/composer.json
index b4e3f11e0f..8a5636baa2 100644
--- a/src/Symfony/Component/WebLink/composer.json
+++ b/src/Symfony/Component/WebLink/composer.json
@@ -39,5 +39,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Workflow/composer.json b/src/Symfony/Component/Workflow/composer.json
index c46201872f..333b82ce57 100644
--- a/src/Symfony/Component/Workflow/composer.json
+++ b/src/Symfony/Component/Workflow/composer.json
@@ -38,5 +38,5 @@
         "psr-4": { "Symfony\\Component\\Workflow\\": "" }
     },
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Component/Yaml/composer.json b/src/Symfony/Component/Yaml/composer.json
index daa33c577a..dd7786b071 100644
--- a/src/Symfony/Component/Yaml/composer.json
+++ b/src/Symfony/Component/Yaml/composer.json
@@ -39,5 +39,5 @@
         "Resources/bin/yaml-lint"
     ],
     "minimum-stability": "dev",
-    "version": "5.1-dev"
+    "version": "5.1.x-dev"
 }
diff --git a/src/Symfony/Contracts/Cache/composer.json b/src/Symfony/Contracts/Cache/composer.json
index c3c00d8770..b9b4241fb9 100644
--- a/src/Symfony/Contracts/Cache/composer.json
+++ b/src/Symfony/Contracts/Cache/composer.json
@@ -32,5 +32,5 @@
             "url": "https://github.com/symfony/contracts"
         }
     },
-    "version": "2.1-dev"
+    "version": "2.1.x-dev"
 }
diff --git a/src/Symfony/Contracts/Deprecation/composer.json b/src/Symfony/Contracts/Deprecation/composer.json
index da1d9daadb..a76c31057f 100644
--- a/src/Symfony/Contracts/Deprecation/composer.json
+++ b/src/Symfony/Contracts/Deprecation/composer.json
@@ -23,5 +23,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "2.1-dev"
+    "version": "2.1.x-dev"
 }
diff --git a/src/Symfony/Contracts/EventDispatcher/composer.json b/src/Symfony/Contracts/EventDispatcher/composer.json
index 4f36fb78c8..0243de84d5 100644
--- a/src/Symfony/Contracts/EventDispatcher/composer.json
+++ b/src/Symfony/Contracts/EventDispatcher/composer.json
@@ -32,5 +32,5 @@
             "url": "https://github.com/symfony/contracts"
         }
     },
-    "version": "2.1-dev"
+    "version": "2.1.x-dev"
 }
diff --git a/src/Symfony/Contracts/HttpClient/composer.json b/src/Symfony/Contracts/HttpClient/composer.json
index a7c92c0a3a..86932f5acb 100644
--- a/src/Symfony/Contracts/HttpClient/composer.json
+++ b/src/Symfony/Contracts/HttpClient/composer.json
@@ -31,5 +31,5 @@
             "url": "https://github.com/symfony/contracts"
         }
     },
-    "version": "2.1-dev"
+    "version": "2.1.x-dev"
 }
diff --git a/src/Symfony/Contracts/Service/composer.json b/src/Symfony/Contracts/Service/composer.json
index 0975c5e25b..7be006560c 100644
--- a/src/Symfony/Contracts/Service/composer.json
+++ b/src/Symfony/Contracts/Service/composer.json
@@ -32,5 +32,5 @@
             "url": "https://github.com/symfony/contracts"
         }
     },
-    "version": "2.1-dev"
+    "version": "2.1.x-dev"
 }
diff --git a/src/Symfony/Contracts/Translation/composer.json b/src/Symfony/Contracts/Translation/composer.json
index aa8c1f8096..2027f62c04 100644
--- a/src/Symfony/Contracts/Translation/composer.json
+++ b/src/Symfony/Contracts/Translation/composer.json
@@ -31,5 +31,5 @@
             "url": "https://github.com/symfony/contracts"
         }
     },
-    "version": "2.1-dev"
+    "version": "2.1.x-dev"
 }
diff --git a/src/Symfony/Contracts/composer.json b/src/Symfony/Contracts/composer.json
index 181ce91442..585a2e6beb 100644
--- a/src/Symfony/Contracts/composer.json
+++ b/src/Symfony/Contracts/composer.json
@@ -47,5 +47,5 @@
         ]
     },
     "minimum-stability": "dev",
-    "version": "2.1-dev"
+    "version": "2.1.x-dev"
 }