diff --git a/composer.json b/composer.json
index faf06b3..cc79d52 100644
--- a/composer.json
+++ b/composer.json
@@ -44,8 +44,8 @@
         }
     },
     "require-dev": {
-        "friendsofphp/php-cs-fixer": "^3.64",
-        "phpstan/phpstan": "^1.12",
+        "friendsofphp/php-cs-fixer": "^3.65",
+        "phpstan/phpstan": "^2.0",
         "phpunit/phpunit" : "^9.6"
     },
     "scripts": {
diff --git a/lib/Serializer/functions.php b/lib/Serializer/functions.php
index a6105a9..9b4bbb8 100644
--- a/lib/Serializer/functions.php
+++ b/lib/Serializer/functions.php
@@ -147,7 +147,7 @@ function repeatingElements(Writer $writer, array $items, string $childElementNam
  *
  * You can even mix the two array syntaxes.
  *
- * @param string|int|float|bool|array<int|string, mixed>|object $value
+ * @param string|int|float|bool|array<int|string, mixed>|object|null $value
  */
 function standardSerializer(Writer $writer, $value): void
 {
@@ -181,7 +181,7 @@ function standardSerializer(Writer $writer, $value): void
                 // This item has a numeric index. We just loop through the
                 // array and throw it back in the writer.
                 standardSerializer($writer, $item);
-            } elseif (is_string($name) && is_array($item) && isset($item['attributes'])) {
+            } elseif (is_array($item) && isset($item['attributes'])) {
                 // The key is used for a name, but $item has 'attributes' and
                 // possibly 'value'
                 $writer->startElement($name);
diff --git a/phpstan-baseline.neon b/phpstan-baseline.neon
index 364905f..ec0c143 100644
--- a/phpstan-baseline.neon
+++ b/phpstan-baseline.neon
@@ -1,2 +1,6 @@
 parameters:
-	ignoreErrors:
+  ignoreErrors:
+  -
+    message: "#^Call to function is_null\\(\\) with null will always evaluate to true\\.$#"
+    path: lib/Serializer/functions.php
+    count: 1
diff --git a/tests/Sabre/Xml/ReaderTest.php b/tests/Sabre/Xml/ReaderTest.php
index df2902f..7677ab2 100644
--- a/tests/Sabre/Xml/ReaderTest.php
+++ b/tests/Sabre/Xml/ReaderTest.php
@@ -339,7 +339,7 @@ public function testParseProblem(): void
             $output = $reader->parse();
             $this->fail('We expected a ParseException to be thrown');
         } catch (LibXMLException $e) {
-            self::assertIsArray($e->getErrors());
+            self::assertNotEmpty($e->getErrors());
         }
     }
 
diff --git a/tests/Sabre/Xml/ServiceTest.php b/tests/Sabre/Xml/ServiceTest.php
index 245366f..8559116 100644
--- a/tests/Sabre/Xml/ServiceTest.php
+++ b/tests/Sabre/Xml/ServiceTest.php
@@ -182,9 +182,6 @@ public function testEmptyPropfind(string $xml): void
         $util->namespaceMap = [
             'http://sabre.io/ns' => 'stdClass',
         ];
-        /**
-         * @var PropFindTestAsset
-         */
         $result = $util->expect('{DAV:}propfind', $xml);
         self::assertIsObject($result);
         self::assertInstanceOf(PropFindTestAsset::class, $result);