diff --git a/src/Geometry/Circle.php b/src/Geometry/Circle.php
index 841d6a96..0180d82b 100644
--- a/src/Geometry/Circle.php
+++ b/src/Geometry/Circle.php
@@ -5,7 +5,7 @@ namespace Intervention\Image\Geometry;
 class Circle extends Ellipse
 {
     public function __construct(
-        int $diameter,
+        protected int $diameter,
         protected ?Point $pivot = null
     ) {
         $this->setWidth($diameter);