diff --git a/composer.json b/composer.json
index c82f2281..32595e2a 100644
--- a/composer.json
+++ b/composer.json
@@ -23,7 +23,7 @@
         "sort-packages": true
     },
     "require": {
-        "php": "^7.2",
+        "php": "^7.2 || ^8.0 <8.1",
         "ext-fileinfo": "*",
         "ext-iconv": "*",
         "ext-imap": "*",
diff --git a/src/PhpImap/DataPartInfo.php b/src/PhpImap/DataPartInfo.php
index 173d1e59..b02c1c94 100644
--- a/src/PhpImap/DataPartInfo.php
+++ b/src/PhpImap/DataPartInfo.php
@@ -109,8 +109,7 @@ protected function convertEncodingAfterFetch(): string
     {
         if (isset($this->charset) and !empty(\trim($this->charset))) {
             $this->data = $this->mail->decodeMimeStr(
-                (string) $this->data, // Data to convert
-                (string) \trim($this->charset)
+                (string) $this->data // Data to convert
             );
         }
 
diff --git a/src/PhpImap/Mailbox.php b/src/PhpImap/Mailbox.php
index 7f58a74e..a3e47d74 100644
--- a/src/PhpImap/Mailbox.php
+++ b/src/PhpImap/Mailbox.php
@@ -1332,7 +1332,6 @@ public function downloadAttachment(DataPartInfo $dataInfo, array $params, object
      * Decodes a mime string.
      *
      * @param string $string MIME string to decode
-     * @param string|null $charsetPreferred The charset of the data part info if it was set
      *
      * @return string Converted string if conversion was successful, or the original string if not
      *
@@ -1340,7 +1339,7 @@ public function downloadAttachment(DataPartInfo $dataInfo, array $params, object
      *
      * @todo update implementation pending resolution of https://github.com/vimeo/psalm/issues/2619 & https://github.com/vimeo/psalm/issues/2620
      */
-    public function decodeMimeStr(string $string, ?string $charsetPreferred = null): string
+    public function decodeMimeStr(string $string): string
     {
         $newString = '';
         /** @var list<object{charset?:string, text?:string}>|false */
@@ -1354,7 +1353,7 @@ public function decodeMimeStr(string $string, ?string $charsetPreferred = null):
             $charset = \strtolower($element->charset);
 
             if ('default' === $charset) {
-                $charset = !empty($charsetPreferred) ? $charsetPreferred : $this->decodeMimeStrDefaultCharset;
+                $charset = $this->decodeMimeStrDefaultCharset;
             }
 
             switch ($charset) {