diff --git a/classes/cachemanager.php b/classes/cachemanager.php
index a2e8d80..78fe7a7 100644
--- a/classes/cachemanager.php
+++ b/classes/cachemanager.php
@@ -79,6 +79,9 @@ public static function build_backlink_cache(int $courseid = 0) {
             $coursepageurl = course_get_format($module->course)->get_view_url($module->sectionnum);
             $coursepageurl->set_anchor('module-' . $module->id);
             foreach ($placestore->places as $place) {
+                if (!isset($place->linkedActivity)) {
+                    continue;
+                }
                 $url = !empty($module->showdescription) ?
                     $coursepageurl->out() :
                     new \moodle_url('/mod/learningmap/view.php', ['id' => $module->id]);
diff --git a/classes/task/fill_backlink_cache.php b/classes/task/fill_backlink_cache.php
index a5e05cf..3274bbb 100644
--- a/classes/task/fill_backlink_cache.php
+++ b/classes/task/fill_backlink_cache.php
@@ -49,7 +49,7 @@ public function execute() {
         $fillstate = $cache->get('fillstate');
 
         // If the cache is filled within the last 24 hours, do nothing.
-        if (!empty($fillstate) && $fillstate < time() - 60 * 60 * 24) {
+        if (!empty($fillstate) && $fillstate > time() - 60 * 60 * 24) {
             mtrace('Backlink cache is already filled within the last 24 hours. Exiting.');
             return;
         }