diff --git a/src/Rules/AllowedFile.php b/src/Rules/AllowedFile.php
index e968eeece4..62c71f4c40 100644
--- a/src/Rules/AllowedFile.php
+++ b/src/Rules/AllowedFile.php
@@ -8,7 +8,7 @@
 
 class AllowedFile implements ValidationRule
 {
-    const EXTENSIONS = [
+    private const EXTENSIONS = [
         '7z',
         'aiff',
         'asc',