diff --git a/mod/lesson/locallib.php b/mod/lesson/locallib.php
index 160d80f89cb..4e02e441fc5 100644
--- a/mod/lesson/locallib.php
+++ b/mod/lesson/locallib.php
@@ -2955,7 +2955,7 @@ abstract class lesson_page extends lesson_base {
         for ($i = 0; $i < $this->lesson->maxanswers; $i++) {
             $answer = clone($newanswer);
 
-            if (!empty($properties->answer_editor[$i])) {
+            if (isset($properties->answer_editor[$i])) {
                 if (is_array($properties->answer_editor[$i])) {
                     // Multichoice and true/false pages have an HTML editor.
                     $answer->answer = $properties->answer_editor[$i]['text'];