diff --git a/backend/ldapOperations.js b/backend/ldapOperations.js
index a7faac3..943fff2 100644
--- a/backend/ldapOperations.js
+++ b/backend/ldapOperations.js
@@ -178,7 +178,8 @@ async function createADUser({ ou, vorname, nachname, email, username, password,
     sAMAccountName = sAMAccountName.substring(0, 20);
 
     // userAccountControl: 514 = NORMAL_ACCOUNT + ACCOUNTDISABLE
-    const userAccountControl = 514;
+    // ldapts requires attribute values as strings (numbers cause "The string argument must be of type string" error)
+    const userAccountControl = '514';
     const effectiveDisplayName = displayName || (nachname + ', ' + vorname);
 
     const entry = {
@@ -254,13 +255,14 @@ async function createADUser({ ou, vorname, nachname, email, username, password,
     console.log('[LDAP] Passwort gesetzt für:', dn);
 
     // Step 3: Enable the account (userAccountControl: 512 = NORMAL_ACCOUNT, enabled)
+    // ldapts requires attribute values as strings
     try {
       await client.modify(dn, [
         new Change({
           operation: 'replace',
           modification: new Attribute({
             type: 'userAccountControl',
-            values: [512],
+            values: ['512'],
           }),
         }),
       ]);