diff --git a/src/Entity/Project.php b/src/Entity/Project.php
index 8820ebdd..fb3523d2 100644
--- a/src/Entity/Project.php
+++ b/src/Entity/Project.php
@@ -111,8 +111,8 @@ class Project implements EntityWithMetaFields, EntityWithBudget
      *
      * @Exporter\Expose(label="label.orderNumber")
      *
-     * @ORM\Column(name="order_number", type="text", length=20, nullable=true)
-     * @Assert\Length(max=20)
+     * @ORM\Column(name="order_number", type="text", length=50, nullable=true)
+     * @Assert\Length(max=50)
      */
     private $orderNumber;
     /**
diff --git a/src/Migrations/Version20211008092010.php b/src/Migrations/Version20211008092010.php
new file mode 100644
index 00000000..eb7bbc52
--- /dev/null
+++ b/src/Migrations/Version20211008092010.php
@@ -0,0 +1,40 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the Kimai time-tracking app.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace DoctrineMigrations;
+
+use App\Doctrine\AbstractMigration;
+use Doctrine\DBAL\Schema\Schema;
+
+/**
+ * @version 1.16
+ */
+final class Version20211008092010 extends AbstractMigration
+{
+    public function getDescription(): string
+    {
+        return 'Extend field orderNumber from 20 to 50 characters.';
+    }
+
+    public function up(Schema $schema): void
+    {
+        $projects = $schema->getTable('kimai2_projects');
+        $column = $projects->getColumn('order_number');
+        $column->setOptions(['length' => 50]);
+    }
+
+    public function down(Schema $schema): void
+    {
+        $projects = $schema->getTable('kimai2_projects');
+        $column = $projects->getColumn('order_number');
+        $column->setOptions(['length' => 20]);
+    }
+}
diff --git a/tests/API/ProjectControllerTest.php b/tests/API/ProjectControllerTest.php
index 092399e8..2d1d5c00 100644
--- a/tests/API/ProjectControllerTest.php
+++ b/tests/API/ProjectControllerTest.php
@@ -289,6 +289,7 @@ class ProjectControllerTest extends APIControllerBaseTest
             'end' => '2020-02-08T21:11:42',
             'budget' => '999',
             'timeBudget' => '7200',
+            'orderNumber' => '1234567890/WXYZ/SUBPROJECT/1234/CONTRACT/EMPLOYEE1',
         ];
         $this->request($client, '/api/projects', 'POST', [], json_encode($data));
         $this->assertTrue($client->getResponse()->isSuccessful());
@@ -300,6 +301,7 @@ class ProjectControllerTest extends APIControllerBaseTest
         self::assertEquals('2018-02-08T13:02:54+0000', $result['orderDate']);
         self::assertEquals('2019-02-01T19:32:17+0000', $result['start']);
         self::assertEquals('2020-02-08T21:11:42+0000', $result['end']);
+        self::assertEquals('1234567890/WXYZ/SUBPROJECT/1234/CONTRACT/EMPLOYEE1', $result['orderNumber']);
     }
 
     public function testPostActionWithLeastFields()