diff --git a/htdocs/core/class/extrafields.class.php b/htdocs/core/class/extrafields.class.php
index 33b36b9dd47..14bb1fb6bf1 100644
--- a/htdocs/core/class/extrafields.class.php
+++ b/htdocs/core/class/extrafields.class.php
@@ -1268,11 +1268,12 @@ class ExtraFields
 					require_once DOL_DOCUMENT_ROOT.'/categories/class/categorie.class.php';
 					$data = $form->select_all_categories(Categorie::$MAP_ID_TO_CODE[$InfoFieldList[5]], '', 'parent', 64, $InfoFieldList[6], 1, 1);
 					$out .= '<option value="0">&nbsp;</option>';
-					$dataArray = str_split($data); // as $data is not traversable as it's a string
-					foreach ($dataArray as $data_key => $data_value) {
-						$out .= '<option value="'.$data_key.'"';
-						$out .= ($value == $data_key ? ' selected' : '');
-						$out .= '>'.$data_value.'</option>';
+					if (is_array($data)) {
+						foreach ($data as $data_key => $data_value) {
+							$out .= '<option value="'.$data_key.'"';
+							$out .= ($value == $data_key ? ' selected' : '');
+							$out .= '>'.$data_value.'</option>';
+						}
 					}
 				}
 			}