diff --git a/lib/adminlib.php b/lib/adminlib.php
index 0e80d7c07d2..3a156375a06 100644
--- a/lib/adminlib.php
+++ b/lib/adminlib.php
@@ -3682,12 +3682,15 @@ class admin_setting_configmultiselect extends admin_setting_configselect {
         if (!is_array($data)) {
             return ''; //ignore it
         }
-        if (!$this->load_choices() or empty($this->choices)) {
-            return '';
-        }
 
         unset($data['xxxxx']);
 
+        // Only reject when the caller actually supplied a value
+        // and there is no valid choices to validate against.
+        if (!empty($data) && (!$this->load_choices() || empty($this->choices))) {
+            return '';
+        }
+
         $save = array();
         foreach ($data as $value) {
             if (!array_key_exists($value, $this->choices)) {