diff --git a/web/ui/app.js b/web/ui/app.js
index ea7ca75..de9be09 100644
--- a/web/ui/app.js
+++ b/web/ui/app.js
@@ -428,9 +428,13 @@ async function browseISO() {
 
   try {
     const resp = await fetch(`${API}/disk/partitions?iso=${encodeURIComponent(iso)}`)
+    if (!resp.ok) {
+      status.textContent = 'HTTP ' + resp.status
+      return
+    }
     const data = await resp.json()
-    if (data.error) {
-      status.textContent = data.error
+    if (!data || data.error) {
+      status.textContent = (data && data.error) || 'server error'
       return
     }
     status.textContent = data.length + ' partition' + (data.length === 1 ? '' : 's')
@@ -454,9 +458,13 @@ async function selectPartition(iso, part) {
 
   try {
     const resp = await fetch(`${API}/disk/volumes?iso=${encodeURIComponent(iso)}&part=${encodeURIComponent(part)}`)
+    if (!resp.ok) {
+      volsEl.innerHTML = '<span class="no-files">HTTP ' + resp.status + '</span>'
+      return
+    }
     const data = await resp.json()
-    if (data.error) {
-      volsEl.innerHTML = '<span class="no-files">' + data.error + '</span>'
+    if (!data || data.error) {
+      volsEl.innerHTML = '<span class="no-files">' + (data && data.error ? data.error : 'server error') + '</span>'
       return
     }
     if (!Array.isArray(data) || data.length === 0) {
@@ -464,7 +472,7 @@ async function selectPartition(iso, part) {
       return
     }
     volsEl.innerHTML = data.map(v => `
-      <div class="vol-item" data-action="tag-vol" data-iso="${esc(iso)}" data-part="${esc(part)}" data-vol="${esc(v.Name)}">${esc(v.Name)}</div>
+      <div class="vol-item" data-action="tag-vol" data-iso="${esc(iso)}" data-part="${esc(part)}" data-vol="${esc(v.name)}">${esc(v.name)}</div>
     `).join('')
   } catch (e) {
     volsEl.innerHTML = 'Failed: ' + e.message
@@ -480,9 +488,13 @@ async function viewVolumeTags(iso, part, vol) {
 
   try {
     const resp = await fetch(`${API}/volume/tags?iso=${encodeURIComponent(iso)}&part=${encodeURIComponent(part)}&vol=${encodeURIComponent(vol)}`)
+    if (!resp.ok) {
+      detailEl.innerHTML = '<span class="no-files">HTTP ' + resp.status + '</span>'
+      return
+    }
     const data = await resp.json()
-    if (data.error) {
-      detailEl.innerHTML = '<span class="no-files">' + data.error + '</span>'
+    if (!data || data.error) {
+      detailEl.innerHTML = '<span class="no-files">' + (data && data.error ? data.error : 'server error') + '</span>'
       return
     }
     if (!Array.isArray(data) || data.length === 0) {