diff --git a/CHANGELOG.md b/CHANGELOG.md
index 575247d4..e9f0438c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Fixed
 
+- Fix default value format for multiple dropdown (GLPIObject)
 - Increased the maximum length of the language column to support longer locale codes
 
 ## [1.21.24] - 2025-10-10
diff --git a/inc/field.class.php b/inc/field.class.php
index 7f5383d6..8ac10838 100644
--- a/inc/field.class.php
+++ b/inc/field.class.php
@@ -249,7 +249,7 @@ public function prepareInputForAdd($input)
         $input['name'] = $this->prepareName($input);
 
         if ($input['multiple'] ?? false) {
-            $input['default_value'] = json_encode($input['default_value'] ?? []);
+            $input['default_value'] = json_encode($input['default_value'] ?: []);
         }
 
         //reject adding when field name is too long for mysql