diff --git a/tests/Infection/TrinaryLogicMutatorTest.php b/tests/Infection/TrinaryLogicMutatorTest.php
index 8f1e734..82414b6 100644
--- a/tests/Infection/TrinaryLogicMutatorTest.php
+++ b/tests/Infection/TrinaryLogicMutatorTest.php
@@ -62,6 +62,22 @@ public static function mutationsProvider(): iterable
 				$trinary = \PHPStan\TrinaryLogic::createYes();
 				$trinary->maybe();
 				PHP
+,
+		];
+
+		yield 'It mutates IsSuperTypeOfResult yes' => [
+			<<<'PHP'
+				<?php
+				$trinary = \PHPStan\Type\IsSuperTypeOfResult::createYes();
+				$trinary->yes();
+				PHP
+,
+			<<<'PHP'
+				<?php
+
+				$trinary = \PHPStan\Type\IsSuperTypeOfResult::createYes();
+				!$trinary->no();
+				PHP
 ,
 		];
 	}