diff --git a/__tests__/bundle/emptyConfigDocument.test.ts b/__tests__/bundle/emptyConfigDocument.test.ts
new file mode 100644
index 00000000..1c228256
--- /dev/null
+++ b/__tests__/bundle/emptyConfigDocument.test.ts
@@ -0,0 +1,61 @@
+import type { FakeGithub } from './fakeGithub'
+import { Buffer } from 'node:buffer'
+import { afterAll, afterEach, beforeAll, describe, expect, it, vi } from 'vitest'
+
+import labelFileContents from '../fixtures/labels/labelFileContentsResp.json'
+import { start } from './fakeGithub'
+import { comment, configReads, helpersFor, repo, repoLabels, token } from './helpers'
+import { runBundle } from './runBundle'
+
+vi.setConfig({ testTimeout: 30_000 })
+
+const issueRead = `GET ${repo}/issues/1`
+const labelsRead = `GET ${repo}/labels?per_page=100`
+const labelWrite = `POST ${repo}/issues/1/labels`
+
+function yamlFile(text: string) {
+  const file = structuredClone(labelFileContents)
+  file.content = Buffer.from(text).toString('base64')
+  return file
+}
+
+// the empty-document arm of parseProwConfig (src/utils/config.ts: `loaded === undefined || loaded === null` ->
+// `{}`), driven through dist/index.js: a blank .github/prow.yaml is a found configuration source with no
+// sections, which is not the same as having no file at all; a comment-only file is the same case (issue #393)
+describe('dist/index.js with an empty .github/prow.yaml', () => {
+  let gh: FakeGithub
+  const { expectRequests } = helpersFor(() => gh)
+
+  beforeAll(async () => {
+    gh = await start()
+  })
+  afterEach(() => gh.reset())
+  afterAll(() => gh.close())
+
+  function run(yaml: string, body: string, command: string) {
+    gh.route('GET', `${repo}/contents/.github%2Fprow.yaml`, { status: 200, body: yamlFile(yaml) })
+    gh.route('GET', `${repo}/issues/1`, { status: 200, body: { labels: [] } })
+    gh.route('GET', `${repo}/labels`, repoLabels('lifecycle/stale'))
+    gh.route('POST', `${repo}/issues/1/labels`, { status: 200, body: [] })
+    return runBundle({
+      eventName: 'issue_comment',
+      payload: comment(body),
+      inputs: { ...token, 'prow-commands': command },
+      apiUrl: gh.url,
+    })
+  }
+
+  it.each([
+    ['a blank file', ''],
+    ['a comment-only file', '# prow configuration\n# nothing enabled yet\n'],
+  ])('%s stops the repository tier search and serves /lifecycle from the built-in defaults', async (_name, yaml) => {
+    const result = await run(yaml, '/lifecycle stale', '/lifecycle')
+
+    expect(result.status, result.stdout).toBe(0)
+    expect(result.errors).toEqual([])
+    expect(result.stdout).toContain('lifecycle: using built-in labels frozen,stale,rotten')
+    expect(gh.requestsMatching('POST', /\/issues\/1\/labels$/).map(r => r.body)).toEqual([{ labels: ['lifecycle/stale'] }])
+    // the empty file is a found source: the loader reads no further repository path and never reports "no prow configuration found"
+    expectRequests(configReads({ repo: '.github/prow.yaml' }), [issueRead, labelsRead, labelWrite])
+  })
+})