diff --git a/CHANGELOG.md b/CHANGELOG.md
index 33218656b..7bcb29b95 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -32,6 +32,7 @@
     * Added root page support for `Flex Pages`
     * Added support for more advanced ACL
     * Added `$grav->dispatchEvent()` method for PSR-14 events
+    * Added `flatten_array` filter to form field validation
 1. [](#improved)
     * Twig filter `|yaml_serialize`: added support for `JsonSerializable` objects and other array-like objects
     * Added support for returning Flex Page specific permissions for admin and testing
diff --git a/system/src/Grav/Common/Data/Validation.php b/system/src/Grav/Common/Data/Validation.php
index 1bc186613..d7447209c 100644
--- a/system/src/Grav/Common/Data/Validation.php
+++ b/system/src/Grav/Common/Data/Validation.php
@@ -661,6 +661,19 @@ class Validation
         return !($options && array_diff($value, $options));
     }
 
+    /**
+     * @param mixed $value
+     * @param array $params
+     * @param array $field
+     * @return array|null
+     */
+    protected static function filterFlatten_array($value, $params, $field)
+    {
+        $value = static::filterArray($value, $params, $field);
+
+        return Utils::arrayUnflattenDotNotation($value);
+    }
+
     /**
      * @param mixed $value
      * @param array $params