diff --git a/classes/Quiz.php b/classes/Quiz.php
index 0a72721960..7e063734ed 100644
--- a/classes/Quiz.php
+++ b/classes/Quiz.php
@@ -2297,7 +2297,7 @@ public static function render_sidebar_nav( WP_Post $quiz, $can_access, $tutor_cu
 	 * @since 4.0.5
 	 */
 	public static function sanitize_quiz_content( $content ) {
-		if ( empty( $content ) ) {
+		if ( null === $content || '' === $content ) {
 			return '';
 		}