diff --git a/phpseclib/bootstrap.php b/phpseclib/bootstrap.php
index 0da0999f..547688f9 100644
--- a/phpseclib/bootstrap.php
+++ b/phpseclib/bootstrap.php
@@ -7,7 +7,8 @@
 
 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.'