diff --git a/backend/Testing/Browser/SandboxPageTests.cs b/backend/Testing/Browser/SandboxPageTests.cs
index d74e77e41..b59b44d24 100644
--- a/backend/Testing/Browser/SandboxPageTests.cs
+++ b/backend/Testing/Browser/SandboxPageTests.cs
@@ -53,5 +53,6 @@ await Page.RunAndWaitForResponseAsync(async () =>
             await Page.GetByText("Fetch 500").ClickAsync();
         }, "/api/testing/test500NoException");
         ExpectDeferredException<UnexpectedResponseException>();
+        await Expect(Page.Locator(".modal-box.bg-error:has-text('Internal Server Error (500)')")).ToBeVisibleAsync();
     }
 }
diff --git a/frontend/src/hooks.client.ts b/frontend/src/hooks.client.ts
index 5160b2bd3..30e638bd0 100644
--- a/frontend/src/hooks.client.ts
+++ b/frontend/src/hooks.client.ts
@@ -63,11 +63,18 @@ function shouldTryAutoReload(updateDetected: boolean): boolean {
  */
 handleFetch(async ({ fetch, args }) => {
   const response = await traceFetch(() => fetch(...args));
+
   if (response.status === 401 && location.pathname !== '/login') {
     throw redirect(307, '/logout');
   }
+
+  if (response.status >= 500) {
+    throw new Error(`Unexpected response: ${response.statusText} (${response.status}). URL: ${response.url}.`);
+  }
+
   if (response.headers.get('lexbox-refresh-jwt') == 'true') {
     await invalidate(USER_LOAD_KEY);
   }
+
   return response;
 });