diff --git a/mod/lesson/lang/en/lesson.php b/mod/lesson/lang/en/lesson.php
index a8201a9ab61..93c921bab55 100644
--- a/mod/lesson/lang/en/lesson.php
+++ b/mod/lesson/lang/en/lesson.php
@@ -158,6 +158,7 @@ $string['endoflesson'] = 'End of lesson';
 $string['enteredthis'] = 'entered this.';
 $string['entername'] = 'Enter a nickname for the high scores list';
 $string['enterpassword'] = 'Please enter the password:';
+$string['emptypassword'] = 'Password cannot be empty';
 $string['eolstudentoutoftime'] = 'Attention:  You ran out of time for this lesson.  Your last answer may not have counted if it was answered after the time was up.';
 $string['eolstudentoutoftimenoanswers'] = 'You did not answer any questions.  You have received a 0 for this lesson.';
 $string['essay'] = 'Essay';
diff --git a/mod/lesson/mod_form.php b/mod/lesson/mod_form.php
index b0dbfa7f15d..3b2f1a20a71 100644
--- a/mod/lesson/mod_form.php
+++ b/mod/lesson/mod_form.php
@@ -339,6 +339,9 @@ class mod_lesson_mod_form extends moodleform_mod {
         if (empty($data['maxtime']) and !empty($data['timed'])) {
             $errors['timedgrp'] = get_string('err_numeric', 'form');
         }
+        if (!empty($data['usepassword']) && empty($data['password'])) {
+            $errors['password'] = get_string('emptypassword', 'lesson');
+        }
 
         return $errors;
     }