diff --git a/lib/www/client/source/src/views/Map.vue b/lib/www/client/source/src/views/Map.vue
index d971acc..dcba4e3 100644
--- a/lib/www/client/source/src/views/Map.vue
+++ b/lib/www/client/source/src/views/Map.vue
@@ -627,6 +627,9 @@ export default {
         if (!firstBundle.chunks || typeof firstBundle.chunks !== 'function') {
           throw new Error('Invalid DougalBinaryBundle: chunks method missing');
         }
+        if (!firstBundle.chunks().length) {
+          throw new Error('Invalid DougalBinaryBundle: bundle has no chunks');
+        }
       } catch (e) {
         console.error('Failed to process first sequence:', e);
         return { positions: new Float32Array(0), values: [], udv: 2 };