diff --git a/src/Models/StreamFormat.php b/src/Models/StreamFormat.php
index c48070d..fffaf35 100644
--- a/src/Models/StreamFormat.php
+++ b/src/Models/StreamFormat.php
@@ -4,24 +4,24 @@
 
 class StreamFormat extends AbstractModel
 {
-    public $itag;
-    public $mimeType;
-    public $width;
-    public $height;
-    public $contentLength;
-    public $quality;
-    public $qualityLabel;
-    public $audioQuality;
-    public $audioSampleRate;
-    public $url;
-    public $signatureCipher;
+    public ?int $itag = null;
+    public ?string $mimeType = null;
+    public ?int $width = null;
+    public ?int $height = null;
+    public ?string $contentLength = null;
+    public ?string $quality = null;
+    public ?string $qualityLabel = null;
+    public ?string $audioQuality = null;
+    public ?string $audioSampleRate = null;
+    public ?string $url = null;
+    public ?string $signatureCipher = null;
 
-    public function getCleanMimeType()
+    public function getCleanMimeType(): ?string
     {
         return trim(preg_replace('/;.*/', '', $this->mimeType));
     }
 
-    public function hasRateBypass()
+    public function hasRateBypass(): bool
     {
         return strpos($this->url, 'ratebypass') !== false;
     }