diff --git a/frontend/src/App.jsx b/frontend/src/App.jsx
index 64e4f53..02d560a 100644
--- a/frontend/src/App.jsx
+++ b/frontend/src/App.jsx
@@ -94,7 +94,10 @@ async function fetchJson(path, signal) {
     signal,
     headers: { Accept: 'application/json' },
   })
-  const body = await response.json().catch(() => null)
+  const contentType = response.headers.get('content-type') || ''
+  const body = contentType.includes('application/json')
+    ? await response.json().catch(() => null)
+    : null
 
   if (!response.ok) {
     const error = new Error(body?.error || `Request failed with ${response.status}`)
@@ -103,6 +106,14 @@ async function fetchJson(path, signal) {
     throw error
   }
 
+  if (!body) {
+    const error = new Error(`Expected JSON from ${path}`)
+    error.status = response.status
+    error.path = path
+    error.contentType = contentType
+    throw error
+  }
+
   return body
 }
 
@@ -115,7 +126,7 @@ async function fetchPublicJson(source, signal) {
     return await fetchJson(source.staticPath, signal)
   } catch (error) {
     if (signal?.aborted || error?.name === 'AbortError') throw error
-    if (error?.status === 404) missingStaticDataPaths.add(source.staticPath)
+    if (error?.status === 404 || error?.contentType) missingStaticDataPaths.add(source.staticPath)
     return fetchJson(source.apiPath, signal)
   }
 }