diff --git a/lib/adminlib.php b/lib/adminlib.php
index d15b8d288a6..ca40b5e16fc 100644
--- a/lib/adminlib.php
+++ b/lib/adminlib.php
@@ -2433,6 +2433,19 @@ class admin_setting_confightmleditor extends admin_setting_configtextarea {
         $editor->use_editor($this->get_id(), array('noclean'=>true));
         return parent::output_html($data, $query);
     }
+
+    /**
+     * Checks if data has empty html.
+     *
+     * @param string $data
+     * @return string Empty when no errors.
+     */
+    public function write_setting($data) {
+        if (trim(html_to_text($data)) === '') {
+            $data = '';
+        }
+        return parent::write_setting($data);
+    }
 }
 
 
diff --git a/lib/db/upgrade.php b/lib/db/upgrade.php
index bb8f36a6015..27732f79a4e 100644
--- a/lib/db/upgrade.php
+++ b/lib/db/upgrade.php
@@ -3078,5 +3078,17 @@ function xmldb_main_upgrade($oldversion) {
         upgrade_main_savepoint(true, 2018120303.16);
     }
 
+    if ($oldversion < 2018120305.04) {
+        // Update the empty tag instructions to null.
+        $instructions = get_config('core', 'auth_instructions');
+
+        if (trim(html_to_text($instructions)) === '') {
+            set_config('auth_instructions', '');
+        }
+
+        // Main savepoint reached.
+        upgrade_main_savepoint(true, 2018120305.04);
+    }
+
     return true;
 }
diff --git a/version.php b/version.php
index 5fe0cd50fc0..e65ae952316 100644
--- a/version.php
+++ b/version.php
@@ -29,7 +29,7 @@
 
 defined('MOODLE_INTERNAL') || die();
 
-$version  = 2018120305.03;              // 20181203      = branching date YYYYMMDD - do not modify!
+$version  = 2018120305.04;              // 20181203      = branching date YYYYMMDD - do not modify!
                                         //         RR    = release increments - 00 in DEV branches.
                                         //           .XX = incremental changes.