diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0f73fe82..2d4389cd 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 - Fixed PHP8.1 deprecation errors in modifiers (upper, explode, number_format and replace) [#755](https://github.com/smarty-php/smarty/pull/755) and [#788](https://github.com/smarty-php/smarty/pull/788)
+- Fixed PHP8.1 deprecation errors in capitalize modifier [#789](https://github.com/smarty-php/smarty/issues/789)
 - Fixed use of `rand()` without a parameter in math function [#794](https://github.com/smarty-php/smarty/issues/794)
 
 ## [4.2.0] - 2022-08-01
diff --git a/libs/plugins/modifier.capitalize.php b/libs/plugins/modifier.capitalize.php
index c5fc400a..b7da0898 100644
--- a/libs/plugins/modifier.capitalize.php
+++ b/libs/plugins/modifier.capitalize.php
@@ -22,6 +22,8 @@
  */
 function smarty_modifier_capitalize($string, $uc_digits = false, $lc_rest = false)
 {
+	$string = (string) $string;
+
     if (Smarty::$_MBSTRING) {
         if ($lc_rest) {
             // uppercase (including hyphenated words)