diff --git a/src/Http/ServerRequest.php b/src/Http/ServerRequest.php
index 8ed087747d9..0e0a19560b7 100644
--- a/src/Http/ServerRequest.php
+++ b/src/Http/ServerRequest.php
@@ -1765,10 +1765,10 @@ public function getEnv($key, $default = null)
      * Set a value to the request's environment data.
      *
      * @param string $key The key you want to write to.
-     * @param string|null $value Value to set. Default null.
+     * @param string $value Value to set
      * @return $this
      */
-    public function setEnv($key, $value = null)
+    public function setEnv($key, $value)
     {
         $this->_environment[$key] = $value;
         $this->clearDetectorCache();