diff --git a/src/Interfaces/StreamInterface.php b/src/Interfaces/StreamInterface.php
index dd9a114..70cb7de 100644
--- a/src/Interfaces/StreamInterface.php
+++ b/src/Interfaces/StreamInterface.php
@@ -44,5 +44,5 @@ interface StreamInterface
      *
      * @return void
      */
-    public function close();
+    public function close(): void;
 }