diff --git a/rector.php b/rector.php
index 0a1ebd3..c2fe993 100644
--- a/rector.php
+++ b/rector.php
@@ -12,6 +12,6 @@
     ]);
     $rectorConfig->rule(InlineConstructorDefaultToPropertyRector::class);
     $rectorConfig->sets([
-    LevelSetList::UP_TO_PHP_81
+    LevelSetList::UP_TO_PHP_82
     ]);
 };
diff --git a/src/PHPePub/Helpers/StringHelper.php b/src/PHPePub/Helpers/StringHelper.php
index cb2faa3..00661ac 100644
--- a/src/PHPePub/Helpers/StringHelper.php
+++ b/src/PHPePub/Helpers/StringHelper.php
@@ -33,7 +33,7 @@ public static function fixEncoding($in_str)
         if (mb_detect_encoding($in_str) == "UTF-8" && mb_check_encoding($in_str, "UTF-8")) {
             return $in_str;
         } else {
-            return utf8_encode($in_str);
+            return mb_convert_encoding($in_str, 'UTF-8', 'ISO-8859-1');
         }
     }