diff --git a/phpseclib/bootstrap.php b/phpseclib/bootstrap.php
index bd4ba0b5..5829d328 100644
--- a/phpseclib/bootstrap.php
+++ b/phpseclib/bootstrap.php
@@ -11,7 +11,8 @@
  */
 if (extension_loaded('mbstring')) {
     // 2 - MB_OVERLOAD_STRING
-    if (ini_get('mbstring.func_overload') & 2) {
+    // mbstring.func_overload is deprecated in php 7.2 and removed in php 8.0.
+    if (version_compare(PHP_VERSION, '8.0.0') < 0 && ini_get('mbstring.func_overload') & 2) {
         throw new UnexpectedValueException(
             'Overloading of string functions using mbstring.func_overload ' .
             'is not supported by phpseclib.'