diff --git a/static/js/upcoming.js b/static/js/upcoming.js
index 64daf96..d978c7e 100644
--- a/static/js/upcoming.js
+++ b/static/js/upcoming.js
@@ -206,7 +206,15 @@ document.addEventListener("DOMContentLoaded", () => {
 
   const table = document.getElementById("upcoming");
   fetch(ics)
-    .then(response => response.text())
+    .then(response => {
+      // Without this an error page would be handed to the parser below, which
+      // then fails with a confusing complaint about the calendar syntax.
+      if (!response.ok) {
+        throw new Error(`${ics}: ${response.status} ${response.statusText}`);
+      }
+
+      return response.text();
+    })
     .then(icsText => {
       getUpcomingEvents(icsText, now, max_items, max_days).forEach(event => {
         const row = document.createElement("tr");
@@ -246,5 +254,6 @@ document.addEventListener("DOMContentLoaded", () => {
 
         table.appendChild(row);
       });
-    });
+    })
+    .catch(err => console.error("Fehler beim Laden der Termine:", err));
 });