diff --git a/CHANGELOG.md b/CHANGELOG.md
index 233952fe40..79f1d5dea3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Fixed
 
 - Fix generate associated item massive action
+- Prevent invalid references and non-existent classes during generate item flow.
 - Update locales
 
 
diff --git a/inc/link.class.php b/inc/link.class.php
index 8af76df2a8..9af3c3015a 100644
--- a/inc/link.class.php
+++ b/inc/link.class.php
@@ -148,7 +148,8 @@ public function showItemGenerationForm($params)
                     $row['template_name'] = "";
                 }
 
-                if (Toolbox::hasTrait($itemtype, AssignableItem::class)) {
+                // GLPI 11 safety: skip non-existent classes (e.g. uninstalled plugins like GenericObject)
+                if (class_exists($itemtype) && Toolbox::hasTrait($itemtype, AssignableItem::class)) {
                     $row['assignableitem'] = true;
                     if (!is_array($row['groups_id'])) {
                         $row['groups_id'] = $row['groups_id'] > 0 ? [$row['groups_id']] : [];
@@ -174,7 +175,7 @@ public function showItemGenerationForm($params)
             'active_entities' => $_SESSION['glpiactiveentities'] ?? [],
             'item_rows' => $item_rows,
             'order_web_dir' => $order_web_dir,
-            'assignableitem' => Toolbox::hasTrait($itemtype, AssignableItem::class),
+            'assignableitem' => class_exists($itemtype) && Toolbox::hasTrait($itemtype, AssignableItem::class),
         ]);
         return null;
     }
diff --git a/inc/reference.class.php b/inc/reference.class.php
index a54866540b..36e101151d 100644
--- a/inc/reference.class.php
+++ b/inc/reference.class.php
@@ -471,7 +471,14 @@ public function checkIfTemplateExistsInEntity($detailID, $itemtype, $entity)
         } else {
             $row = $result->current();
             $item = getItemForItemtype($itemtype);
-            $item->getFromDB($row["templates_id"]);
+            if (
+                $item === false
+                || (int) $row["templates_id"] === 0
+                || !$item->getFromDB($row["templates_id"])
+            ) {
+                return 0;
+            }
+
             if ($item->getField('entities_id') == $entity
             || ($item->maybeRecursive()
             && $item->fields['is_recursive']