diff --git a/grade/grading/form/rubric/lib.php b/grade/grading/form/rubric/lib.php
index 361e73beecb..a5783156642 100644
--- a/grade/grading/form/rubric/lib.php
+++ b/grade/grading/form/rubric/lib.php
@@ -386,7 +386,7 @@ class gradingform_rubric_controller extends gradingform_controller {
     public function get_options() {
         $options = self::get_default_options();
         if (!empty($this->definition->options)) {
-            $thisoptions = json_decode($this->definition->options);
+            $thisoptions = json_decode($this->definition->options, true); // Assoc. array is expected.
             foreach ($thisoptions as $option => $value) {
                 $options[$option] = $value;
             }