diff --git a/composer.json b/composer.json
index 260b7d9..97048ae 100644
--- a/composer.json
+++ b/composer.json
@@ -23,7 +23,6 @@
     }
   },
   "require-dev": {
-    "guzzlehttp/psr7": "^1",
     "ipl/stdlib": "dev-main",
     "ipl/i18n": "dev-main"
   }
diff --git a/src/ValidatorChain.php b/src/ValidatorChain.php
index 1044498..3917d2b 100644
--- a/src/ValidatorChain.php
+++ b/src/ValidatorChain.php
@@ -68,7 +68,7 @@ public function add(Validator $validator, $breakChainOnFailure = false, $priorit
         $this->validators->insert($validator, $priority);
 
         if ($breakChainOnFailure) {
-            $this->validatorsThatBreakTheChain->attach($validator);
+            $this->validatorsThatBreakTheChain->offsetSet($validator);
         }
 
         return $this;
@@ -227,7 +227,7 @@ public function merge(ValidatorChain $validatorChain)
          * @var  Validator $validator
          */
         foreach ($validatorChain->validators->yieldAll() as $priority => $validator) {
-            $this->add($validator, $validatorsThatBreakTheChain->contains($validator), $priority);
+            $this->add($validator, $validatorsThatBreakTheChain->offsetExists($validator), $priority);
         }
 
         return $this;
@@ -282,7 +282,7 @@ public function isValid($value): bool
 
             $this->addMessages($validator->getMessages());
 
-            if ($this->validatorsThatBreakTheChain->contains($validator)) {
+            if ($this->validatorsThatBreakTheChain->offsetExists($validator)) {
                 break;
             }
         }
diff --git a/tests/FileValidatorTest.php b/tests/FileValidatorTest.php
index 92d0f9c..bb3e5ca 100644
--- a/tests/FileValidatorTest.php
+++ b/tests/FileValidatorTest.php
@@ -2,22 +2,69 @@
 
 namespace ipl\Tests\Validator;
 
-use GuzzleHttp\Psr7\UploadedFile;
 use ipl\I18n\NoopTranslator;
 use ipl\I18n\StaticTranslator;
 use ipl\Validator\FileValidator;
+use Psr\Http\Message\StreamInterface;
+use Psr\Http\Message\UploadedFileInterface;
+use RuntimeException;
 
 class FileValidatorTest extends TestCase
 {
-    public function createUploadedFileObject($mimeType = 'application/pdf'): UploadedFile
-    {
-        return new UploadedFile(
-            'test/test.pdf',
-            500,
-            0,
-            'test.pdf',
-            $mimeType
-        );
+    public function createUploadedFileObject(
+        string $filename = 'test.pdf',
+        int $size = 500,
+        int $error = UPLOAD_ERR_OK,
+        string $mimeType = 'application/pdf'
+    ): UploadedFileInterface {
+        return new class ($filename, $size, $error, $mimeType) implements UploadedFileInterface {
+            private readonly int $size;
+            private readonly int $error;
+            private readonly string $clientFilename;
+            private readonly string $clientMediaType;
+
+            public function __construct(
+                string $clientFilename,
+                int $size,
+                int $error,
+                string $clientMediaType
+            ) {
+                $this->size = $size;
+                $this->error = $error;
+                $this->clientFilename = $clientFilename;
+                $this->clientMediaType = $clientMediaType;
+            }
+
+            public function getStream(): StreamInterface
+            {
+                throw new RuntimeException('not implemented');
+            }
+
+            public function moveTo(string $targetPath): void
+            {
+                throw new RuntimeException('not implemented');
+            }
+
+            public function getSize(): ?int
+            {
+                return $this->size;
+            }
+
+            public function getError(): int
+            {
+                return $this->error;
+            }
+
+            public function getClientFilename(): ?string
+            {
+                return $this->clientFilename;
+            }
+
+            public function getClientMediaType(): ?string
+            {
+                return $this->clientMediaType;
+            }
+        };
     }
 
     public function testValidValue(): void
@@ -89,7 +136,7 @@ public function testMimeTypeOption(): void
         $this->assertTrue($validator->isValid($uploadedFile));
 
         $validator->setAllowedMimeTypes(['image/gif', 'image/jpeg']);
-        $uploadedFile = $this->createUploadedFileObject('image/png');
+        $uploadedFile = $this->createUploadedFileObject(mimeType: 'image/png');
 
         $this->assertFalse($validator->isValid($uploadedFile));
     }
diff --git a/tests/ValidatorChainTest.php b/tests/ValidatorChainTest.php
index 59224ac..f2544e2 100644
--- a/tests/ValidatorChainTest.php
+++ b/tests/ValidatorChainTest.php
@@ -273,7 +273,7 @@ public function testMerge()
         $this->assertSame($callbackValidator, $validatorsAsArray[0]);
         $this->assertInstanceOf(TestValidator::class, $validatorsAsArray[1]);
         $this->assertInstanceOf(CallbackValidator::class, $validatorsAsArray[2]);
-        $this->assertTrue($validators->getValidatorsThatBreakTheChain()->contains($callbackValidator));
+        $this->assertTrue($validators->getValidatorsThatBreakTheChain()->offsetExists($callbackValidator));
     }
 
     public function testArraySpecExceptionIfNameIsMissing()