diff --git a/src/Expectations/OppositeExpectation.php b/src/Expectations/OppositeExpectation.php
index aa7edcb8..07284e1f 100644
--- a/src/Expectations/OppositeExpectation.php
+++ b/src/Expectations/OppositeExpectation.php
@@ -84,7 +84,7 @@ final class OppositeExpectation
     {
         return Targeted::make(
             $this->original,
-            fn (ObjectDescription $object): bool => ! preg_match('/^<\?php\s+declare\(.*?strict_types\s?=\s?1.*?\);/', (string) file_get_contents($object->path)),
+            fn (ObjectDescription $object): bool => ! (bool) preg_match('/^<\?php\s+declare\(.*?strict_types\s?=\s?1.*?\);/', (string) file_get_contents($object->path)),
             'not to use strict types',
             FileLineFinder::where(fn (string $line): bool => str_contains($line, '<?php')),
         );