diff --git a/src/Normalizer/SlugNormalizer.php b/src/Normalizer/SlugNormalizer.php
index d41ea24c17..7cfb960e3c 100644
--- a/src/Normalizer/SlugNormalizer.php
+++ b/src/Normalizer/SlugNormalizer.php
@@ -51,6 +51,7 @@ public function normalize(string $text, array $context = []): string
             $slug = \mb_substr($slug, 0, $length, 'UTF-8');
         }
 
+        // @phpstan-ignore-next-line Because it thinks mb_substr() returns false on PHP 7.4
         return $slug;
     }
 }