diff --git a/app-code/api/account/update_passkey.php b/app-code/api/account/update_passkey.php
index 5adedf0..5a3d1d2 100644
--- a/app-code/api/account/update_passkey.php
+++ b/app-code/api/account/update_passkey.php
@@ -166,7 +166,7 @@ try {
         $data->userDisplayName = $userDisplayName;
 
         // Store registration data in the database
-	$credentialId = $data->credentialId instanceof \lbuchs\WebAuthn\Binary\ByteBuffer ? $data->credentialId->getBinaryString() : $data->credentialId;
+	$credentialId = $data->credentialId instanceof \lbuchs\WebAuthn\Binary\ByteBuffer ? $data->credentialId->getBinaryString() : (string)$data->credentialId;
 	$credentialPublicKey = $data->credentialPublicKey;
 	$signatureCounter = (int)$data->signatureCounter;
 	$stmt = $conn->prepare("UPDATE users set  credential_id = ?, public_key = ?, counter = ?, auth_method_enabled_passkey = 1, auth_method_required_passkey = 1 WHERE username = ?");
@@ -187,7 +187,7 @@ try {
 } catch (Throwable $ex) {
     $return = new stdClass();
     $return->success = false;
-    $return->msg = 'Passkey registration failed: ' . $ex->getMessage();
+    $return->msg = 'Passkey registration failed: ' . $ex->getMessage() . ' (credentialId type: ' . (is_object($data->credentialId ?? null) ? get_class($data->credentialId) : gettype($data->credentialId ?? null)) . ')';
 
     header('Content-Type: application/json');
     print(json_encode($return));