diff --git a/CHANGES.md b/CHANGES.md
index 1a537239b725499150649412fd9db284fd89ad42..e2959f7a6876d3c92debcf7e6ec631e6debdda86 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -4,6 +4,10 @@ moodle-theme_boost_campus_child
 Changes
 -------
 
+### Unreleased
+
+* 2021-01-06 - Improvement: Declare which major stable version of Moodle this plugin supports (see MDL-59562 for details).
+
 ### v3.9-r1
 
 * 2020-10-06 - Prepare compatibility for Moodle 3.9.
diff --git a/version.php b/version.php
index fc6f888d93f7cd74b83ec931599819ce67cd6262..75e1e31f59fd627a9ed4e54479b4d4f089f15a58 100644
--- a/version.php
+++ b/version.php
@@ -28,5 +28,6 @@ $plugin->component = 'theme_boost_campus_child';
 $plugin->version = 2020100700;
 $plugin->release = 'v3.9-r1';
 $plugin->requires = 2020061500;
+$plugin->supported = [39, 39];
 $plugin->maturity = MATURITY_STABLE;
 $plugin->dependencies = array('theme_boost' => 2020061500, 'theme_boost_campus' => 2020093000);