diff --git a/composer.json b/composer.json
index 37fc0a82..f51bfef1 100644
--- a/composer.json
+++ b/composer.json
@@ -42,7 +42,7 @@
         "propel/propel1": "^1.6",
         "psalm/plugin-phpunit": "^0.16",
         "psalm/plugin-symfony": "^3.0",
-        "rector/rector": "^0.13",
+        "rector/rector": "^0.15",
         "symfony/config": "^4.4 || ^5.4 || ^6.0",
         "symfony/dependency-injection": "^4.4 || ^5.4 || ^6.0",
         "symfony/http-foundation": "^4.4 || ^5.4 || ^6.0",
diff --git a/src/Writer/InMemoryWriter.php b/src/Writer/InMemoryWriter.php
index 1d30c0d6..ef66f6af 100644
--- a/src/Writer/InMemoryWriter.php
+++ b/src/Writer/InMemoryWriter.php
@@ -18,7 +18,7 @@ final class InMemoryWriter implements WriterInterface
     /**
      * @var array<mixed>
      */
-    private $elements;
+    private array $elements = [];
 
     public function open(): void
     {
diff --git a/src/Writer/SitemapWriter.php b/src/Writer/SitemapWriter.php
index 7b90c2b5..f5f33e89 100644
--- a/src/Writer/SitemapWriter.php
+++ b/src/Writer/SitemapWriter.php
@@ -134,7 +134,7 @@ public function close(): void
      */
     public static function generateSitemapIndex(string $folder, string $baseUrl, string $pattern = 'sitemap*.xml', string $filename = 'sitemap.xml'): void
     {
-        $content = "<?xml version='1.0' encoding='UTF-8'?".">\n<sitemapindex xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xsi:schemaLocation='http://www.sitemaps.org/schemas/sitemap/1.0 http://www.sitemaps.org/schemas/sitemap/0.9/siteindex.xsd' xmlns='http://www.sitemaps.org/schemas/sitemap/0.9'>\n";
+        $content = "<?xml version='1.0' encoding='UTF-8'?>\n<sitemapindex xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xsi:schemaLocation='http://www.sitemaps.org/schemas/sitemap/1.0 http://www.sitemaps.org/schemas/sitemap/0.9/siteindex.xsd' xmlns='http://www.sitemaps.org/schemas/sitemap/0.9'>\n";
         foreach (glob(sprintf('%s/%s', $folder, $pattern)) as $file) {
             $stat = stat($file);
             $content .= sprintf(
@@ -250,7 +250,7 @@ private function fixDataType(array &$data): void
      */
     private function generateDefaultLine(array $data): string
     {
-        return sprintf('    '.'<url><loc>%s</loc><lastmod>%s</lastmod><changefreq>%s</changefreq><priority>%s</priority></url>'."\n", $data['url'], date('Y-m-d', strtotime($data['lastmod'])), $data['changefreq'], $data['priority']);
+        return sprintf('    <url><loc>%s</loc><lastmod>%s</lastmod><changefreq>%s</changefreq><priority>%s</priority></url>'."\n", $data['url'], date('Y-m-d', strtotime($data['lastmod'])), $data['changefreq'], $data['priority']);
     }
 
     /**
@@ -281,7 +281,7 @@ private function generateImageLine(array $data): string
             $images .= '</image:image>';
         }
 
-        return sprintf('    '.'<url><loc>%s</loc>%s</url>'."\n", $data['url'], $images);
+        return sprintf('    <url><loc>%s</loc>%s</url>'."\n", $data['url'], $images);
     }
 
     /**
@@ -300,7 +300,7 @@ private function generateVideoLine(array $data): string
             $videos .= sprintf('<video:%1$s>%2$s</video:%1$s>', $builder[$key] ?? $key, $video);
         }
 
-        return sprintf('    '.'<url><loc>%s</loc><video:video>%s</video:video></url>'."\n", $data['url'], $videos);
+        return sprintf('    <url><loc>%s</loc><video:video>%s</video:video></url>'."\n", $data['url'], $videos);
     }
 
     /**
diff --git a/tests/Source/DoctrineODMQuerySourceIteratorTest.php b/tests/Source/DoctrineODMQuerySourceIteratorTest.php
index a00a39d9..a52e168c 100644
--- a/tests/Source/DoctrineODMQuerySourceIteratorTest.php
+++ b/tests/Source/DoctrineODMQuerySourceIteratorTest.php
@@ -85,7 +85,7 @@ private function createConfiguration(): Configuration
         $config->setHydratorNamespace('Hydrators');
         $config->setPersistentCollectionDir($directory);
         $config->setPersistentCollectionNamespace('PersistentCollections');
-        $config->setMetadataDriverImpl($config->newDefaultAnnotationDriver()); // @phpstan-ignore-line
+        $config->setMetadataDriverImpl($config->newDefaultAnnotationDriver());
 
         return $config;
     }
diff --git a/tests/Source/IteratorSourceIteratorTest.php b/tests/Source/IteratorSourceIteratorTest.php
index 4a1be3a7..5b5e12cf 100644
--- a/tests/Source/IteratorSourceIteratorTest.php
+++ b/tests/Source/IteratorSourceIteratorTest.php
@@ -24,7 +24,7 @@ final class IteratorSourceIteratorTest extends TestCase
     /**
      * @var \Iterator<mixed, mixed>&MockObject
      */
-    private $iterator;
+    private \Iterator $iterator;
 
     protected function setUp(): void
     {