diff --git a/src/Auth/Process/AttributeAddFromLDAP.php b/src/Auth/Process/AttributeAddFromLDAP.php
index 3aac2d93f..3e366fc02 100644
--- a/src/Auth/Process/AttributeAddFromLDAP.php
+++ b/src/Auth/Process/AttributeAddFromLDAP.php
@@ -96,7 +96,7 @@ public function process(array &$state): void
         foreach ($attributes as $attr => $val) {
             $arrSearch[] = '%' . $attr . '%';
 
-            if (is_array($val) && count($val) > 0 && strlen($val[0]) > 0) {
+            if (is_array($val) && count($val) > 0 && is_string($val[0]) && strlen($val[0]) > 0) {
                 $arrReplace[] = $this->connector->escapeFilterValue($val[0], true);
             } else {
                 $arrReplace[] = '';