diff --git a/src/UploadedFile.php b/src/UploadedFile.php
index 1b9e3d4..0624179 100644
--- a/src/UploadedFile.php
+++ b/src/UploadedFile.php
@@ -104,8 +104,8 @@ public function __construct(
         $streamOrFile,
         int $size,
         int $error,
-        string $clientFilename = null,
-        string $clientMediaType = null
+        ?string $clientFilename = null,
+        ?string $clientMediaType = null
     ) {
         if (!array_key_exists($error, self::ERRORS)) {
             throw new InvalidArgumentException(sprintf(
diff --git a/src/UploadedFileFactory.php b/src/UploadedFileFactory.php
index ad7d658..5238055 100644
--- a/src/UploadedFileFactory.php
+++ b/src/UploadedFileFactory.php
@@ -17,10 +17,10 @@ final class UploadedFileFactory implements UploadedFileFactoryInterface
      */
     public function createUploadedFile(
         StreamInterface $stream,
-        int $size = null,
+        ?int $size = null,
         int $error = UPLOAD_ERR_OK,
-        string $clientFilename = null,
-        string $clientMediaType = null
+        ?string $clientFilename = null,
+        ?string $clientMediaType = null
     ): UploadedFileInterface {
         $size = (int) ($size === null ? $stream->getSize() : $size);
         return new UploadedFile($stream, $size, $error, $clientFilename, $clientMediaType);