diff --git a/index.php b/index.php
index 52feab3..1d06380 100644
--- a/index.php
+++ b/index.php
@@ -76,11 +76,15 @@ function loadJsonFile(string $file, array $default): array
 
 function saveJsonFile(string $file, array $data): void
 {
-    file_put_contents(
-        $file,
-        json_encode($data, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE),
-        LOCK_EX
-    );
+    $json = json_encode($data, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE);
+    if ($json === false) {
+        throw new RuntimeException('Konfiguration konnte nicht kodiert werden.');
+    }
+
+    $written = @file_put_contents($file, $json, LOCK_EX);
+    if ($written === false) {
+        throw new RuntimeException('Konfiguration konnte nicht gespeichert werden. Bitte Dateirechte prüfen.');
+    }
 }
 
 function isAdminLoggedIn(): bool