diff --git a/blog/index.php b/blog/index.php
index b3a11a2bc87..d4baa2f8f0c 100644
--- a/blog/index.php
+++ b/blog/index.php
@@ -116,7 +116,7 @@ if ($courseid != SITEID) {
 }
 
 if (!empty($userid)) {
-    $user = core_user::get_user($userid);
+    $user = core_user::get_user($userid, '*', MUST_EXIST);
     $PAGE->navigation->extend_for_user($user);
 }
 
@@ -153,10 +153,11 @@ if ($usernode && $courseid != SITEID) {
 if ($courseid != SITEID) {
     $PAGE->set_heading($course->fullname);
     echo $OUTPUT->header();
-    $backurl = new moodle_url('/user/view.php', ['id' => $userid, 'course' => $courseid]);
-    echo $OUTPUT->single_button($backurl, get_string('back'), 'get', ['class' => 'mb-3']);
 
     if (!empty($user)) {
+        $backurl = new moodle_url('/user/view.php', ['id' => $user->id, 'course' => $courseid]);
+        echo $OUTPUT->single_button($backurl, get_string('back'), 'get', ['class' => 'mb-3']);
+
         $headerinfo = array('heading' => fullname($user), 'user' => $user);
         echo $OUTPUT->context_header($headerinfo, 2);
     }