diff --git a/src/Geometry/Polygon.php b/src/Geometry/Polygon.php
index e7bee7bc5..244dd7ce4 100644
--- a/src/Geometry/Polygon.php
+++ b/src/Geometry/Polygon.php
@@ -106,7 +106,7 @@ public function offsetExists($offset): bool
      * @param mixed $offset
      * @return Point
      */
-    public function offsetGet($offset)
+    public function offsetGet($offset): mixed
     {
         return $this->points[$offset];
     }