diff --git a/mod/lesson/format.php b/mod/lesson/format.php
index 5ff51bf8f41..ecdc2932f85 100644
--- a/mod/lesson/format.php
+++ b/mod/lesson/format.php
@@ -503,7 +503,7 @@ class qformat_default {
     }
 
 
-    function readquestion($lines) {
+    protected function readquestion($lines) {
     /// Given an array of lines known to define a question in
     /// this format, this function converts it into a question
     /// object suitable for processing and insertion into Moodle.