diff --git a/mod/quiz/editlib.php b/mod/quiz/editlib.php
index feb74b70b88..acd51d0208b 100644
--- a/mod/quiz/editlib.php
+++ b/mod/quiz/editlib.php
@@ -90,7 +90,7 @@ function quiz_delete_empty_page($layout, $index) {
  */
 function quiz_add_quiz_question($id, &$quiz, $page = 0) {
     global $DB;
-    $questions = explode(',', $quiz->questions);
+    $questions = explode(',', quiz_clean_layout($quiz->questions));
     if (in_array($id, $questions)) {
         return false;
     }
@@ -101,7 +101,7 @@ function quiz_add_quiz_question($id, &$quiz, $page = 0) {
         $end = end($breaks);
         $last = prev($breaks);
         $last = $last ? $last : -1;
-        if (!$quiz->questionsperpage || (($end - $last -1) < $quiz->questionsperpage)) {
+        if (!$quiz->questionsperpage || (($end - $last - 1) < $quiz->questionsperpage)) {
             array_pop($questions);
         }
     }
diff --git a/mod/quiz/locallib.php b/mod/quiz/locallib.php
index 07fbc6e9cbe..42a6f66a01c 100644
--- a/mod/quiz/locallib.php
+++ b/mod/quiz/locallib.php
@@ -301,7 +301,7 @@ function quiz_number_of_pages($layout) {
  * @return integer The number of questions in the quiz.
  */
 function quiz_number_of_questions_in_quiz($layout) {
-    $layout = quiz_questions_in_quiz($layout);
+    $layout = quiz_questions_in_quiz(quiz_clean_layout($layout));
     $count = substr_count($layout, ',');
     if ($layout !== '') {
         $count++;
diff --git a/mod/quiz/simpletest/testlocallib.php b/mod/quiz/simpletest/testlocallib.php
index 60cd6e4a7d6..7f93b89431d 100644
--- a/mod/quiz/simpletest/testlocallib.php
+++ b/mod/quiz/simpletest/testlocallib.php
@@ -48,6 +48,7 @@ class quiz_locallib_test extends UnitTestCase {
         $this->assertEqual(quiz_number_of_questions_in_quiz('1,2,3,0'), 3);
         $this->assertEqual(quiz_number_of_questions_in_quiz('1,2,3,0'), 3);
         $this->assertEqual(quiz_number_of_questions_in_quiz('0,1,0,0,2,0'), 2);
+        $this->assertEqual(quiz_number_of_questions_in_quiz('10,,0,0'), 1);
     }
 
     function test_quiz_clean_layout() {