diff --git a/packages/collector-extension/lib/index.js b/packages/collector-extension/lib/index.js
index e363d263a220b3fec7fe3f2ff7f870dcdf69dad5..d9552044e8314a00fd878904a0ebbc0a21ce8180 100644
--- a/packages/collector-extension/lib/index.js
+++ b/packages/collector-extension/lib/index.js
@@ -9,6 +9,7 @@ const getUserCacheDir = require('cache-directory')
 const globStream = require('glob-stream')
 const invariably = { false: () => false, void: () => undefined }
 const ospath = require('path')
+const { posix: path } = ospath
 const runCommand = require('./util/run-command.js')
 const { pipeline, Writable } = require('stream')
 const yaml = require('js-yaml')
@@ -80,7 +81,7 @@ module.exports.register = function () {
             }
           }
           for (const scan of scans) {
-            for (const file of await srcFs(scan.dir, scan.files)) {
+            for (const file of await srcFs(scan.dir, scan.files, scan.base)) {
               let existingFile
               if (file.path === 'antora.yml') {
                 const generated = yaml.load(file.contents)
@@ -154,14 +155,14 @@ function getBaseCacheDir ({ dir: dot, runtime: { cacheDir: preferredDir } }) {
     : expandPath(preferredDir, { dot })
 }
 
-function srcFs (cwd, globs = ['**/*']) {
+function srcFs (cwd, globs = '**/*', base) {
   return new Promise((resolve, reject, cache = Object.create(null), accum = []) => {
     pipeline(
       globStream(globs, Object.assign({ cwd, cache }, GLOB_OPTS)),
       forEach(({ path: abspathPosix }, _, done) => {
         if (cache[abspathPosix].constructor === Array) return done() // detects some directories
         const abspath = ospath.sep === '\\' ? ospath.normalize(abspathPosix) : abspathPosix
-        const relpath = abspath.substr(cwd.length + 1)
+        const relpath = base ? path.join('.', base, abspath.substr(cwd.length + 1)) : abspath.substr(cwd.length + 1)
         fsp.stat(abspath).then(
           (stat) => {
             if (stat.isDirectory()) return done() // detects directories that slipped through cache check
diff --git a/packages/collector-extension/test/collector-extension-test.js b/packages/collector-extension/test/collector-extension-test.js
index 0316cc32ff8354fbef999e470af41501aeab3cfe..167fa1bf07f5292d145e627cc362a117481086fe 100644
--- a/packages/collector-extension/test/collector-extension-test.js
+++ b/packages/collector-extension/test/collector-extension-test.js
@@ -418,7 +418,7 @@ describe('collector extension', () => {
 
     it('should collect files without running command if only scan key is specified', async () => {
       const collectorConfig = {
-        scan: { dir: 'not-docs' },
+        scan: { dir: 'other-docs' },
       }
       await runScenario({
         repoName: 'test-at-start-path',
@@ -435,10 +435,48 @@ describe('collector extension', () => {
       })
     })
 
+    it('should rebase files if base key is set on scan', async () => {
+      const collectorConfig = {
+        scan: { dir: 'code', base: 'modules/extend/examples' },
+      }
+      await runScenario({
+        repoName: 'test-at-start-path',
+        startPath: 'docs',
+        collectorConfig,
+        before: (contentAggregate) => {
+          expect(contentAggregate).to.have.lengthOf(1)
+          expect(contentAggregate[0].files).to.be.empty()
+        },
+        after: (contentAggregate) => {
+          expect(contentAggregate[0].files).to.have.lengthOf(1)
+          expect(contentAggregate[0].files[0].path).to.equal('modules/extend/examples/extended-pdf-converter.rb')
+        },
+      })
+    })
+
+    it('should drop leading / on value of base key', async () => {
+      const collectorConfig = {
+        scan: { dir: 'code', base: '/modules/extend/examples' },
+      }
+      await runScenario({
+        repoName: 'test-at-start-path',
+        startPath: 'docs',
+        collectorConfig,
+        before: (contentAggregate) => {
+          expect(contentAggregate).to.have.lengthOf(1)
+          expect(contentAggregate[0].files).to.be.empty()
+        },
+        after: (contentAggregate) => {
+          expect(contentAggregate[0].files).to.have.lengthOf(1)
+          expect(contentAggregate[0].files[0].path).to.equal('modules/extend/examples/extended-pdf-converter.rb')
+        },
+      })
+    })
+
     it('should collect files from multiple scan dirs', async () => {
       const collectorConfig = {
         run: { command: 'node .gen-start-page.js', dir: '.' },
-        scan: [{ dir: './build' }, { dir: 'not-docs' }],
+        scan: [{ dir: './build' }, { dir: 'other-docs' }],
       }
       await runScenario({
         repoName: 'test-at-start-path',
diff --git a/packages/collector-extension/test/fixtures/test-at-start-path/code/extended-pdf-converter.rb b/packages/collector-extension/test/fixtures/test-at-start-path/code/extended-pdf-converter.rb
new file mode 100644
index 0000000000000000000000000000000000000000..bc6a9252d1c7d24331b277375f4203cf74a8d609
--- /dev/null
+++ b/packages/collector-extension/test/fixtures/test-at-start-path/code/extended-pdf-converter.rb
@@ -0,0 +1,5 @@
+class ExtendedPDFConverter < (Asciidoctor::Converter.for 'pdf')
+  register_for 'pdf'
+
+  # overrides go here
+end
diff --git a/packages/collector-extension/test/fixtures/test-at-start-path/not-docs/modules/ROOT/pages/outside-start-path.adoc b/packages/collector-extension/test/fixtures/test-at-start-path/other-docs/modules/ROOT/pages/outside-start-path.adoc
similarity index 100%
rename from packages/collector-extension/test/fixtures/test-at-start-path/not-docs/modules/ROOT/pages/outside-start-path.adoc
rename to packages/collector-extension/test/fixtures/test-at-start-path/other-docs/modules/ROOT/pages/outside-start-path.adoc