diff --git a/src/UnicodeString.php b/src/UnicodeString.php
index d8947a2..21d2666 100644
--- a/src/UnicodeString.php
+++ b/src/UnicodeString.php
@@ -861,6 +861,8 @@ public function offsetGet($offset): string
 
     /**
      * @inheritDoc
+     *
+     * @return void
      */
     #[\ReturnTypeWillChange]
     public function offsetSet($offset, $value)
@@ -897,6 +899,8 @@ public function offsetSet($offset, $value)
 
     /**
      * @inheritDoc
+     *
+     * @return void
      */
     #[\ReturnTypeWillChange]
     public function offsetUnset($offset)