diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8c48cc26..3982e895 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -19,6 +19,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Fix dependency conflict with GLPI core by no longer vendoring symfony/deprecation-contracts and symfony/polyfill-ctype.
 - Fix default field values not being applied when fields are empty on creation
 - Fix mandatory fields blocking automated item creation
+- Fix unclear mandatory field error when a GLPI form creating a ticket does not provide the field.
 
 ## [1.24.5] - 2026-09-11
 
diff --git a/inc/container.class.php b/inc/container.class.php
index 45afb6ed..9969c275 100644
--- a/inc/container.class.php
+++ b/inc/container.class.php
@@ -1669,10 +1669,11 @@ private static function isMandatoryCheckBypassed(array $data): bool
      * @param array   $data          Data send by form
      * @param string  $itemtype      Item type
      * @param boolean $massiveaction ?
+     * @param boolean $is_creation   True when validating a new item with nothing submitted
      *
      * @return boolean
      */
-    public static function validateValues($data, $itemtype, $massiveaction)
+    public static function validateValues($data, $itemtype, $massiveaction, $is_creation = false)
     {
         /** @var DBmysql $DB */
         global $DB;
@@ -1775,6 +1776,13 @@ public static function validateValues($data, $itemtype, $massiveaction)
         if ($empty_errors !== []) {
             Session::AddMessageAfterRedirect(__('Some mandatory fields are empty', 'fields')
                                           . ' : ' . implode(', ', $empty_errors), false, ERROR);
+            if ($is_creation) {
+                Session::AddMessageAfterRedirect(
+                    __('The form or source creating this item does not provide the mandatory fields above: map them to it, or make them optional.', 'fields'),
+                    false,
+                    ERROR,
+                );
+            }
         }
 
         if ($number_errors !== []) {
@@ -2061,7 +2069,7 @@ private static function checkContainerMandatory(CommonDBTM $item, PluginFieldsCo
             }
         }
 
-        if (self::validateValues($data, $item::getType(), isset($_REQUEST['massiveaction'])) === false) {
+        if (self::validateValues($data, $item::getType(), isset($_REQUEST['massiveaction']), $item->isNewItem()) === false) {
             return false;
         }
 
diff --git a/tests/Units/ContainerItemUpdateTest.php b/tests/Units/ContainerItemUpdateTest.php
index 760ce33e..90367905 100644
--- a/tests/Units/ContainerItemUpdateTest.php
+++ b/tests/Units/ContainerItemUpdateTest.php
@@ -355,6 +355,10 @@ public function testCreateIsBlockedWhenMandatoryDomFieldIsMissing(): void
             __('Some mandatory fields are empty', 'fields'),
             ERROR,
         );
+        $this->hasSessionMessageThatContains(
+            __('The form or source creating this item does not provide the mandatory fields above: map them to it, or make them optional.', 'fields'),
+            ERROR,
+        );
 
         // Creation with the mandatory field filled must succeed.
         $ticket = new Ticket();