diff --git a/mod/quiz/lang/en/quiz.php b/mod/quiz/lang/en/quiz.php
index eec5160c62e..7f25273fc74 100644
--- a/mod/quiz/lang/en/quiz.php
+++ b/mod/quiz/lang/en/quiz.php
@@ -397,6 +397,7 @@ $string['grademethod_help'] = 'When multiple attempts are allowed, the following
 $string['gradesdeleted'] = 'Quiz grades deleted';
 $string['gradesofar'] = '{$a->method}: {$a->mygrade} / {$a->quizgrade}.';
 $string['gradetopassnotset'] = 'This quiz does not have a grade to pass set so you cannot use this option. Please use the require grade setting instead.';
+$string['gradetopassmustbeset'] = 'Grade to pass cannot be zero as this quiz has its completion method set to require passing grade. Please set a non-zero value.';
 $string['gradingdetails'] = 'Marks for this submission: {$a->raw}/{$a->max}.';
 $string['gradingdetailsadjustment'] = 'With previous penalties this gives <strong>{$a->cur}/{$a->max}</strong>.';
 $string['gradingdetailspenalty'] = 'This submission attracted a penalty of {$a}.';
diff --git a/mod/quiz/mod_form.php b/mod/quiz/mod_form.php
index abe9b980004..74029fb5816 100644
--- a/mod/quiz/mod_form.php
+++ b/mod/quiz/mod_form.php
@@ -534,9 +534,15 @@ class mod_quiz_mod_form extends moodleform_mod {
         }
 
         if (array_key_exists('completion', $data) && $data['completion'] == COMPLETION_TRACKING_AUTOMATIC) {
+            $completionpass = isset($data['completionpass']) ? $data['completionpass'] : $this->current->completionpass;
+
             // Show an error if require passing grade was selected and the grade to pass was set to 0.
-            if ($data['completionpass'] == 1 && (empty($data['gradepass']) || grade_floatval($data['gradepass']) == 0)) {
-                $errors['completionpassgroup'] = get_string('gradetopassnotset', 'quiz');
+            if ($completionpass && (empty($data['gradepass']) || grade_floatval($data['gradepass']) == 0)) {
+                if (isset($data['completionpass'])) {
+                    $errors['completionpassgroup'] = get_string('gradetopassnotset', 'quiz');
+                } else {
+                    $errors['gradepass'] = get_string('gradetopassmustbeset', 'quiz');
+                }
             }
         }