diff --git a/course/format/classes/base.php b/course/format/classes/base.php
index 426045e2d87..30ff931c9e9 100644
--- a/course/format/classes/base.php
+++ b/course/format/classes/base.php
@@ -841,16 +841,15 @@ abstract class base {
      * core_courseformat will be user as the component.
      *
      * @param string $key the string key
-     * @param string|object|array $data extra data that can be used within translation strings
-     * @param string|null $lang moodle translation language, null means use current
+     * @param string|object|array|int $data extra data that can be used within translation strings
      * @return string the get_string result
      */
-    public function get_format_string(string $key, $data = null, $lang = null): string {
+    public function get_format_string(string $key, $data = null): string {
         $component = 'format_' . $this->get_format();
         if (!get_string_manager()->string_exists($key, $component)) {
             $component = 'core_courseformat';
         }
-        return get_string($key, $component, $data, $lang);
+        return get_string($key, $component, $data);
     }
 
     /**
diff --git a/course/format/upgrade.txt b/course/format/upgrade.txt
index bd9249216ec..aec45425d04 100644
--- a/course/format/upgrade.txt
+++ b/course/format/upgrade.txt
@@ -2,6 +2,9 @@ This files describes API changes for course formats
 
 Overview of this plugin type at https://moodledev.io/docs/apis/plugintypes/format
 
+=== 4.2.7 ===
+* The core_courseformat\base::get_format_string last parameter has been removed because it was erroneous.
+
 === 4.2 ===
 * New core_courseformat\base::get_context() to get the course context directly from the format instance.
 * New core_courseformat\base::delete_module() method. Now format plugins can extend the activity deletion logic