diff --git a/src/Psalm/Storage/Assertion/IsEqualIsset.php b/src/Psalm/Storage/Assertion/IsEqualIsset.php
index 0ac2e9af920..bded7c5ce06 100644
--- a/src/Psalm/Storage/Assertion/IsEqualIsset.php
+++ b/src/Psalm/Storage/Assertion/IsEqualIsset.php
@@ -4,7 +4,7 @@
 
 use Psalm\Storage\Assertion;
 
-class IsEqualIsset extends Assertion
+final class IsEqualIsset extends Assertion
 {
     /** @psalm-mutation-free */
     public function getNegation(): Assertion