diff --git a/CHANGELOG.md b/CHANGELOG.md
index ed5c87ba..e91d27af 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Changed
+- Used PHPStan's int-mask-of<T> type where applicable ([#779](https://github.com/jsonrainbow/json-schema/pull/779))
 
 ## [6.1.0] - 2025-02-04
 ### Added
@@ -91,4 +93,4 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fix: Clean up `.gitattributes` ([#687](https://github.com/jsonrainbow/json-schema/pull/687))
 - Fix: Order `friendsofphp/php-cs-fixer` rules ([#688](https://github.com/jsonrainbow/json-schema/pull/688))
 - HTTP to HTTPS redirection breaks remote reference resolution ([#709](https://github.com/jsonrainbow/json-schema/pull/709))
-- Corrected several typos and code style issues
\ No newline at end of file
+- Corrected several typos and code style issues
diff --git a/src/JsonSchema/Constraints/BaseConstraint.php b/src/JsonSchema/Constraints/BaseConstraint.php
index a4b4c9a2..0b661e0f 100644
--- a/src/JsonSchema/Constraints/BaseConstraint.php
+++ b/src/JsonSchema/Constraints/BaseConstraint.php
@@ -30,6 +30,7 @@ class BaseConstraint
 
     /**
      * @var int All error types which have occurred
+     * @phpstan-var int-mask-of<Validator::ERROR_*>
      */
     protected $errorMask = Validator::ERROR_NONE;
 
@@ -129,6 +130,7 @@ public function reset()
      * Get the error mask
      *
      * @return int
+     * @phpstan-return int-mask-of<Validator::ERROR_*>
      */
     public function getErrorMask()
     {
diff --git a/src/JsonSchema/Validator.php b/src/JsonSchema/Validator.php
index 86440949..a02c2e5d 100644
--- a/src/JsonSchema/Validator.php
+++ b/src/JsonSchema/Validator.php
@@ -44,7 +44,8 @@ class Validator extends BaseConstraint
      *
      * @return int
      *
-     * @phpstan-param Constraint::CHECK_MODE_* $checkMode
+     * @phpstan-param int-mask-of<Constraint::CHECK_MODE_*> $checkMode
+     * @phpstan-return int-mask-of<Validator::ERROR_*>
      */
     public function validate(&$value, $schema = null, $checkMode = null)
     {