diff --git a/composer.json b/composer.json
index d2d2173..42d5272 100644
--- a/composer.json
+++ b/composer.json
@@ -15,7 +15,8 @@
         }
     },
     "require": {
-        "php": ">=7.2"
+        "php": ">=7.2",
+        "ext-mbstring": "*"
     },
     "require-dev": {
         "phpunit/phpunit": "^8",
diff --git a/src/BencodeTorrent.php b/src/BencodeTorrent.php
index 2a91e87..0b50f3b 100644
--- a/src/BencodeTorrent.php
+++ b/src/BencodeTorrent.php
@@ -45,7 +45,7 @@ class BencodeTorrent extends Bencode
     private function setDelim(): void
     {
         if (self::$utf8_filelist_delim === null) {
-            self::$utf8_filelist_delim = utf8_encode(chr(self::FILELIST_DELIM));
+            self::$utf8_filelist_delim = mb_convert_encoding(chr(self::FILELIST_DELIM), 'UTF-8', 'ISO-8859-1');
         }
     }