diff --git a/mod/quiz/classes/structure.php b/mod/quiz/classes/structure.php
index 342af00a7d2..5f56a8adf1a 100644
--- a/mod/quiz/classes/structure.php
+++ b/mod/quiz/classes/structure.php
@@ -914,6 +914,7 @@ class structure {
         $maxslot = $DB->get_field_sql('SELECT MAX(slot) FROM {quiz_slots} WHERE quizid = ?', array($this->get_quizid()));
 
         $trans = $DB->start_delegated_transaction();
+        $DB->delete_records('quiz_slot_tags', array('slotid' => $slot->id));
         $DB->delete_records('quiz_slots', array('id' => $slot->id));
         for ($i = $slot->slot + 1; $i <= $maxslot; $i++) {
             $DB->set_field('quiz_slots', 'slot', $i - 1,
diff --git a/mod/quiz/lib.php b/mod/quiz/lib.php
index 629edc02f1d..8c8fc91291c 100644
--- a/mod/quiz/lib.php
+++ b/mod/quiz/lib.php
@@ -183,7 +183,9 @@ function quiz_delete_instance($id) {
              WHERE slot.quizid = ? AND q.qtype = ?";
     $questionids = $DB->get_fieldset_sql($sql, array($quiz->id, 'random'));
 
-    // We need to do this before we try and delete randoms, otherwise they would still be 'in use'.
+    // We need to do the following deletes before we try and delete randoms, otherwise they would still be 'in use'.
+    $quizslots = $DB->get_fieldset_select('quiz_slots', 'id', 'quizid = ?', array($quiz->id));
+    $DB->delete_records_list('quiz_slot_tags', 'slotid', $quizslots);
     $DB->delete_records('quiz_slots', array('quizid' => $quiz->id));
     $DB->delete_records('quiz_sections', array('quizid' => $quiz->id));