diff --git a/AbstractBrowser.php b/AbstractBrowser.php
index 43e0602..b1f0a0a 100644
--- a/AbstractBrowser.php
+++ b/AbstractBrowser.php
@@ -53,8 +53,8 @@ abstract class AbstractBrowser
     public function __construct(array $server = [], History $history = null, CookieJar $cookieJar = null)
     {
         $this->setServerParameters($server);
-        $this->history = $history ?: new History();
-        $this->cookieJar = $cookieJar ?: new CookieJar();
+        $this->history = $history ?? new History();
+        $this->cookieJar = $cookieJar ?? new CookieJar();
     }
 
     /**
diff --git a/Response.php b/Response.php
index f4c04c9..23b1a37 100644
--- a/Response.php
+++ b/Response.php
@@ -84,7 +84,7 @@ public function getHeaders(): array
     /**
      * Gets a response header.
      *
-     * @return string|array The first header value if $first is true, an array of values otherwise
+     * @return string|array|null The first header value if $first is true, an array of values otherwise
      */
     public function getHeader(string $header, bool $first = true)
     {