diff --git a/static/index.html b/static/index.html
index 068ab04..adbacdd 100644
--- a/static/index.html
+++ b/static/index.html
@@ -274,8 +274,15 @@ async function init() {
             window.location.href = "/login";
             return;
         }
+        if (!res.ok) {
+            throw new Error("Failed to load files");
+        }
         var files = await res.json();
 
+        if (!Array.isArray(files)) {
+            throw new Error("Invalid response format");
+        }
+
         var sel = document.getElementById("fileSelector");
         sel.innerHTML = "";
         files.forEach(function(f) {