diff --git a/lib/db/upgrade.php b/lib/db/upgrade.php
index 469b6ab62ea..2dc080cf9f0 100644
--- a/lib/db/upgrade.php
+++ b/lib/db/upgrade.php
@@ -2190,29 +2190,6 @@ function xmldb_main_upgrade($oldversion) {
         }
 
         if (!empty($themes)) {
-
-            list($insql, $inparams) = $DB->get_in_or_equal($themes, SQL_PARAMS_NAMED);
-
-            // Replace the theme usage.
-            $DB->set_field_select('course', 'theme', 'clean', "theme $insql", $inparams);
-            $DB->set_field_select('course_categories', 'theme', 'clean', "theme $insql", $inparams);
-            $DB->set_field_select('user', 'theme', 'clean', "theme $insql", $inparams);
-            $DB->set_field_select('mnet_host', 'theme', 'clean', "theme $insql", $inparams);
-
-            // Replace the theme configs.
-            if (in_array(get_config('core', 'theme'), $themes)) {
-                set_config('theme', 'clean');
-            }
-            if (in_array(get_config('core', 'thememobile'), $themes)) {
-                set_config('thememobile', 'clean');
-            }
-            if (in_array(get_config('core', 'themelegacy'), $themes)) {
-                set_config('themelegacy', 'clean');
-            }
-            if (in_array(get_config('core', 'themetablet'), $themes)) {
-                set_config('themetablet', 'clean');
-            }
-
             // Hacky emulation of plugin uninstallation.
             foreach ($themes as $theme) {
                 unset_all_config_for_plugin('theme_' . $theme);