diff --git a/classes/GdLib.php b/classes/GdLib.php
index 6ab7b99..b0f30a9 100644
--- a/classes/GdLib.php
+++ b/classes/GdLib.php
@@ -7,7 +7,7 @@
 
 class GdLib extends Darkroom\GdLib
 {
-    protected function resize(SimpleImage $image, array $options)
+    protected function resize(SimpleImage $image, array $options): SimpleImage
     {
         // clip
         if (isset($options['clip'])) {
@@ -29,4 +29,4 @@ protected function resize(SimpleImage $image, array $options)
 
         return $image->thumbnail($options['width'], $options['height'] ?? $options['width'], $options['crop']);
     }
-}
\ No newline at end of file
+}