diff --git a/src/Methods/CopyMethod.php b/src/Methods/CopyMethod.php
index 38d1114..0184733 100644
--- a/src/Methods/CopyMethod.php
+++ b/src/Methods/CopyMethod.php
@@ -19,7 +19,7 @@ class CopyMethod implements ExposeMethod
      */
     protected $filesystem = null;
 
-    public function __construct(Filesystem $filesystem = null)
+    public function __construct(?Filesystem $filesystem = null)
     {
         $this->filesystem = $filesystem ?: new Filesystem();
     }
diff --git a/src/Methods/SymlinkMethod.php b/src/Methods/SymlinkMethod.php
index bfe9a66..706fe3c 100644
--- a/src/Methods/SymlinkMethod.php
+++ b/src/Methods/SymlinkMethod.php
@@ -17,7 +17,7 @@ class SymlinkMethod implements ExposeMethod
      */
     protected $filesystem = null;
 
-    public function __construct(Filesystem $filesystem = null)
+    public function __construct(?Filesystem $filesystem = null)
     {
         $this->filesystem = $filesystem ?: new Filesystem();
     }