diff --git a/src/Browser.php b/src/Browser.php
index 8a3be5d..61cad85 100644
--- a/src/Browser.php
+++ b/src/Browser.php
@@ -7,17 +7,17 @@
 
 class Browser extends BrowserClient
 {
-    public function setUserAgent($agent)
+    public function setUserAgent($agent): void
     {
         $this->headers['User-Agent'] = $agent;
     }
 
-    public function getUserAgent()
+    public function getUserAgent(): ?string
     {
         return Utils::arrayGet($this->headers, 'User-Agent');
     }
 
-    public function followRedirects($enabled)
+    public function followRedirects($enabled): self
     {
         $this->options[CURLOPT_FOLLOWLOCATION] = $enabled ? 1 : 0;
         return $this;
@@ -44,12 +44,12 @@ public function cachedGet($url)
         return $response;
     }
 
-    protected function getCacheKey($url)
+    protected function getCacheKey($url): string
     {
-        return md5($url) . '_v3';
+        return md5($url) . '_v4';
     }
 
-    public function consentCookies()
+    public function consentCookies(): void
     {
         $response = $this->get('https://www.youtube.com/');
         $current_url = $response->info->url;