diff --git a/src/Illuminate/Http/Request.php b/src/Illuminate/Http/Request.php
index 610d3a50ca17..3515e0399b30 100644
--- a/src/Illuminate/Http/Request.php
+++ b/src/Illuminate/Http/Request.php
@@ -336,7 +336,7 @@ public function replace(array $input)
      * @param  mixed  $default
      * @return mixed
      */
-    public function get($key, $default = null)
+    public function get(string $key, $default = null)
     {
         return parent::get($key, $default);
     }