diff --git a/composer.json b/composer.json
index 71b7fe7cc..9eb39d04b 100644
--- a/composer.json
+++ b/composer.json
@@ -18,7 +18,7 @@
     "amphp/http-server": "^2.1",
     "dms/phpunit-arraysubset-asserts": "dev-master",
     "ergebnis/composer-normalize": "^2.28",
-    "friendsofphp/php-cs-fixer": "3.91.1",
+    "friendsofphp/php-cs-fixer": "3.91.2",
     "mll-lab/php-cs-fixer-config": "5.11.0",
     "nyholm/psr7": "^1.5",
     "phpbench/phpbench": "^1.2",
diff --git a/src/Error/Error.php b/src/Error/Error.php
index 82d20a421..e0bcb65e4 100644
--- a/src/Error/Error.php
+++ b/src/Error/Error.php
@@ -22,7 +22,7 @@
  *
  * @see \GraphQL\Tests\Error\ErrorTest
  */
-class Error extends \Exception implements \JsonSerializable, ClientAware, ProvidesExtensions
+class Error extends \Exception implements \Stringable, \JsonSerializable, ClientAware, ProvidesExtensions
 {
     /**
      * Lazily initialized.
diff --git a/src/Language/AST/Node.php b/src/Language/AST/Node.php
index 6a5d056db..35cac6850 100644
--- a/src/Language/AST/Node.php
+++ b/src/Language/AST/Node.php
@@ -31,7 +31,7 @@
  *
  * @see \GraphQL\Tests\Language\AST\NodeTest
  */
-abstract class Node implements \JsonSerializable
+abstract class Node implements \Stringable, \JsonSerializable
 {
     public ?Location $loc = null;
 
diff --git a/src/Type/Definition/Type.php b/src/Type/Definition/Type.php
index 8dee72b8d..9503848ee 100644
--- a/src/Type/Definition/Type.php
+++ b/src/Type/Definition/Type.php
@@ -9,7 +9,7 @@
 /**
  * Registry of standard GraphQL types and base class for all other types.
  */
-abstract class Type implements \JsonSerializable
+abstract class Type implements \Stringable, \JsonSerializable
 {
     public const INT = 'Int';
     public const FLOAT = 'Float';
diff --git a/tests/Type/ScalarSerializationTest.php b/tests/Type/ScalarSerializationTest.php
index afaf9e740..8221c9a45 100644
--- a/tests/Type/ScalarSerializationTest.php
+++ b/tests/Type/ScalarSerializationTest.php
@@ -111,7 +111,7 @@ public function testSerializesOutputAsString(): void
         self::assertSame('1', $stringType->serialize(true));
         self::assertSame('', $stringType->serialize(false));
         self::assertSame('', $stringType->serialize(null));
-        self::assertSame('foo', $stringType->serialize(new class() {
+        self::assertSame('foo', $stringType->serialize(new class() implements \Stringable {
             public function __toString(): string
             {
                 return 'foo';
diff --git a/tests/Type/TestClasses/ObjectIdStub.php b/tests/Type/TestClasses/ObjectIdStub.php
index 1d3cc43a2..1c6b6d75c 100644
--- a/tests/Type/TestClasses/ObjectIdStub.php
+++ b/tests/Type/TestClasses/ObjectIdStub.php
@@ -2,7 +2,7 @@
 
 namespace GraphQL\Tests\Type\TestClasses;
 
-final class ObjectIdStub
+final class ObjectIdStub implements \Stringable
 {
     private int $id;