diff --git a/question/bank/managecategories/classes/helper.php b/question/bank/managecategories/classes/helper.php
index a742f5a7d20..c531b81a7c7 100644
--- a/question/bank/managecategories/classes/helper.php
+++ b/question/bank/managecategories/classes/helper.php
@@ -168,7 +168,8 @@ class helper {
 
         // Recursively indent the children.
         foreach ($categories[$id]->childids as $childid) {
-            if ($childid != $nochildrenof) {
+            [$childcategory, ] = explode(',', $childid);
+            if ($childcategory != $nochildrenof) {
                 $newcategories = $newcategories + self::flatten_category_tree(
                     $categories,
                     $childid,
diff --git a/question/bank/managecategories/tests/behat/move_question_categories.feature b/question/bank/managecategories/tests/behat/move_question_categories.feature
index 1279686dceb..4ac901dbe96 100644
--- a/question/bank/managecategories/tests/behat/move_question_categories.feature
+++ b/question/bank/managecategories/tests/behat/move_question_categories.feature
@@ -99,3 +99,23 @@ Feature: A teacher can reorder question categories
     And I choose "Move" in the open action menu
     And I click on "After Course category 1" "link" in the "Move Course category 2" "dialogue"
     And I should see "ID number already in use. Change it to move or update category."
+
+  Scenario: Teacher can move a category via the edit form
+    Given "Course category 1" "list_item" should appear before "Course category 2" "list_item"
+    And "Course category 2" "list_item" should appear before "Course category 3" "list_item"
+    When I open the action menu in "Course category 3" "list_item"
+    And I choose "Edit" in the open action menu
+    And I should see "Top for Course 1" in the "Parent category" "select"
+    And I should see "Course category 1" in the "Parent category" "field"
+    And I should see "Course category 2" in the "Parent category" "field"
+    And I should not see "Course category 3" in the "Parent category" "field"
+    And I set the field "Parent category" to "Course category 1"
+    And I press "Save changes"
+    Then "Course category 1" "list_item" should appear before "Course category 3" "list_item"
+    And "Course category 3" "list_item" should appear before "Course category 2" "list_item"
+    And I open the action menu in "Course category 1" "list_item"
+    And I choose "Edit" in the open action menu
+    And I should see "Top for Course 1" in the "Parent category" "select"
+    And I should not see "Course category 1" in the "Parent category" "field"
+    And I should see "Course category 2" in the "Parent category" "field"
+    And I should not see "Course category 3" in the "Parent category" "field"