diff --git a/lib/private/Files/Storage/Wrapper/Encoding.php b/lib/private/Files/Storage/Wrapper/Encoding.php
index 92e20cfb3df03..d6d32aaaf7f9e 100644
--- a/lib/private/Files/Storage/Wrapper/Encoding.php
+++ b/lib/private/Files/Storage/Wrapper/Encoding.php
@@ -37,7 +37,7 @@ public function __construct(array $parameters) {
 	 * Returns whether the given string is only made of ASCII characters
 	 */
 	private function isAscii(string $str): bool {
-		return !preg_match('/[\\x80-\\xff]+/', $str);
+		return mb_check_encoding($str, 'ASCII');
 	}
 
 	/**