diff --git a/admin/renderer.php b/admin/renderer.php
index f4f55b5c7de..024dd614dfd 100644
--- a/admin/renderer.php
+++ b/admin/renderer.php
@@ -220,7 +220,7 @@ class core_admin_renderer extends plugin_renderer_base {
             $output .= $this->container_end();
         }
 
-        $button = new single_button($continueurl, get_string('upgradestart', 'admin'), 'get');
+        $button = new single_button($continueurl, get_string('upgradestart', 'admin'), 'get', true);
         $button->class = 'continuebutton';
         $output .= $this->render($button);
         $output .= $this->footer();
diff --git a/lib/outputcomponents.php b/lib/outputcomponents.php
index 52c291eaa68..1c962d78a3b 100644
--- a/lib/outputcomponents.php
+++ b/lib/outputcomponents.php
@@ -855,6 +855,7 @@ class single_button implements renderable {
      * @param moodle_url $url
      * @param string $label button text
      * @param string $method get or post submit method
+     * @param bool $primary whether this is a primary button, used for styling
      * @param array $attributes Attributes for the HTML button tag
      */
     public function __construct(moodle_url $url, $label, $method='post', $primary=false, $attributes = []) {