diff --git a/app/controllers/course/details.php b/app/controllers/course/details.php
index 2a685e3b683521bf9423906445caeab87633ead0..1c9b03456681bd2270f5db468c9f1fce700f3bfd 100644
--- a/app/controllers/course/details.php
+++ b/app/controllers/course/details.php
@@ -111,7 +111,7 @@ class Course_DetailsController extends AuthenticatedController
                         return false;
                     }
                     $modul_start = Semester::find($modul->start)->beginn ?: 0;
-                    $modul_end = Semester::find($modul->end)->ende ?: PHP_INT_MAX;
+                    $modul_end = $modul->end ? Semester::find($modul->end)->ende : PHP_INT_MAX;
                     return ($modul_start <= $course_end && $modul_end >= $course_start);
                 });
 
diff --git a/lib/models/ModuleManagementModelTreeItem.php b/lib/models/ModuleManagementModelTreeItem.php
index c2d4269c32b0067488d9b16d7cd42877baf8bec8..522a7b05d4069ab0d85d794dce3f1dccc07a7946 100644
--- a/lib/models/ModuleManagementModelTreeItem.php
+++ b/lib/models/ModuleManagementModelTreeItem.php
@@ -57,7 +57,7 @@ abstract class ModuleManagementModelTreeItem extends ModuleManagementModel imple
         $types = $types ?: $path;
         $trails = [];
         $class_name = get_class($this);
-        $next = $path[array_search($class_name, $path) + 1];
+        $next = $path[array_search($class_name, $path) + 1] ?? null;
         $parents = $this->getParents($next);
 
         foreach ($parents as $parent) {