diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9d1c12ae38..6a2f364761 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,8 +5,15 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
+## [unreleased]
+
+### Fixed
+- Fix generate associated item massive action
+
 ## [2.12.6] - 2026-02-23
 
+### Fixed
+
 - Fix SQL query error when displaying deliveries
 - Fix error during generate associated material action
 - Fix SQL warning during installation
diff --git a/inc/link.class.php b/inc/link.class.php
index a7b7953b1e..8af76df2a8 100644
--- a/inc/link.class.php
+++ b/inc/link.class.php
@@ -135,24 +135,26 @@ public function showItemGenerationForm($params)
                     $row['otherserial'] = $item->fields["otherserial"] ?? "";
                     $row['states_id'] = $item->fields["states_id"] ?? "";
                     $row['locations_id'] = $item->fields["locations_id"] ?? "";
-                    $row['groups_id'] = $item->fields["groups_id"] ?? [];
+                    $row['groups_id'] = $item->fields["groups_id"] ?? 0;
                     $row['immo_number'] = $item->fields["immo_number"] ?? "";
                     $row['template_name'] = $reference->getTemplateName($itemtype, $templateID);
-
-                    if (Toolbox::hasTrait($itemtype, AssignableItem::class)) {
-                        $row['assignableitem'] = true;
-                    }
-
                 } else {
                     $row['name'] = false;
                     $row['otherserial'] = false;
                     $row['states_id'] = false;
                     $row['locations_id'] = false;
-                    $row['groups_id'] = [];
+                    $row['groups_id'] = 0;
                     $row['immo_number'] = false;
                     $row['template_name'] = "";
                 }
 
+                if (Toolbox::hasTrait($itemtype, AssignableItem::class)) {
+                    $row['assignableitem'] = true;
+                    if (!is_array($row['groups_id'])) {
+                        $row['groups_id'] = $row['groups_id'] > 0 ? [$row['groups_id']] : [];
+                    }
+                }
+
                 $item_rows[] = $row;
                 $found = true;
             }