diff --git a/src/EventImmutable.php b/src/EventImmutable.php
index fb191a58..01022c9d 100644
--- a/src/EventImmutable.php
+++ b/src/EventImmutable.php
@@ -67,7 +67,8 @@ public function __construct($name, array $arguments = [])
      * @since   1.0
      * @throws  BadMethodCallException
      */
-    public function offsetSet($name, $value): void
+    #[\ReturnTypeWillChange]
+    public function offsetSet($name, $value)
     {
         throw new BadMethodCallException(
             sprintf(
@@ -89,7 +90,8 @@ public function offsetSet($name, $value): void
      *
      * @since   1.0
      */
-    public function offsetUnset($name): void
+    #[\ReturnTypeWillChange]
+    public function offsetUnset($name)
     {
         throw new BadMethodCallException(
             sprintf(