diff --git a/webseite/classes/SubjectData.php b/webseite/classes/SubjectData.php
index b5e2641..7808c13 100644
--- a/webseite/classes/SubjectData.php
+++ b/webseite/classes/SubjectData.php
@@ -243,6 +243,11 @@ class SubjectData
 
     public function setId(string $id): void
     {
+        rename(
+            Config::getSubjectDirectory($this->getId()),
+            Config::getSubjectDirectory($id)
+        );
+
         $this->id = $id;
     }
 
diff --git a/webseite/subjectEditor.php b/webseite/subjectEditor.php
index 429f284..3d1b0d0 100644
--- a/webseite/subjectEditor.php
+++ b/webseite/subjectEditor.php
@@ -63,8 +63,10 @@ if ($_SERVER['REQUEST_METHOD'] == 'POST') {
 
     if (empty($errors)) {
         $newSubject = false;
-        if (isset($allSubjects[$_POST['id']])) {
-            $newSubject = $allSubjects[$_POST['id']];
+        if (isset($allSubjects[$_POST['oldSubjectId']])) {
+            $newSubject = $allSubjects[$_POST['oldSubjectId']];
+
+            $newSubject->setId($_POST['id']);
             $newSubject->setDisplayName($_POST['displayName']);
             $newSubject->setDescription($_POST['description']);
             $newSubject->setColor($_POST['color']);
@@ -129,6 +131,8 @@ if ($_SERVER['REQUEST_METHOD'] == 'POST') {
                        class="w-full px-4 py-3 border rounded-lg focus:outline-none focus:ring-2 focus:ring-blue-500 text-lg enabled:hover:border-gray-400"
                        placeholder="z.B. mathe"
                        value="<?php echo $defaultValues['id'] ?>">
+
+                <input type="hidden" name="oldSubjectId" value="<?php echo $defaultValues['id']; ?>">
             </div>
 
             <div>