diff --git a/README.md b/README.md
index ca8afcb..03a8786 100644
--- a/README.md
+++ b/README.md
@@ -124,7 +124,8 @@ or a file named `.git`.
 Given a path, walk up the file system tree until a git repo working
 directory is found.  Since this calls `stat` a bunch of times, it's
 probably best to only call it if you're reasonably sure you're likely to be
-in a git project somewhere.
+in a git project somewhere. Pass in `opts.root` to stop checking at that
+directory.
 
 Resolves to `null` if not in a git project.
 
diff --git a/lib/find.js b/lib/find.js
index d58f01d..e520ce8 100644
--- a/lib/find.js
+++ b/lib/find.js
@@ -1,15 +1,15 @@
 const is = require('./is.js')
-const { dirname } = require('path')
+const { dirname, sep } = require('path')
 
-module.exports = async ({ cwd = process.cwd() } = {}) => {
-  if (await is({ cwd })) {
-    return cwd
-  }
-  while (cwd !== dirname(cwd)) {
-    cwd = dirname(cwd)
+module.exports = async ({ cwd = process.cwd(), root = sep } = {}) => {
+  while (true) {
     if (await is({ cwd })) {
       return cwd
     }
+    const next = dirname(cwd)
+    if (cwd === root || cwd === next) {
+      return null
+    }
+    cwd = next
   }
-  return null
 }
diff --git a/test/find.js b/test/find.js
index 57d7287..3101912 100644
--- a/test/find.js
+++ b/test/find.js
@@ -1,4 +1,5 @@
 const t = require('tap')
+const { join } = require('path')
 const find = require('../lib/find.js')
 
 t.test('find the git dir many folders up', t => {
@@ -10,6 +11,24 @@ t.test('find the git dir many folders up', t => {
   return t.resolveMatch(find({ cwd: path }), root)
 })
 
+t.test('stop before root dir', t => {
+  const root = t.testdir({
+    '.git': { index: 'hello' },
+    a: { b: { c: { d: { e: {} } } } },
+  })
+  const path = `${root}/a/b/c/d/e`
+  return t.resolveMatch(find({ cwd: path, root: join(root, 'a') }), null)
+})
+
+t.test('stop at root dir', t => {
+  const root = t.testdir({
+    '.git': { index: 'hello' },
+    a: { b: { c: { d: { e: {} } } } },
+  })
+  const path = `${root}/a/b/c/d/e`
+  return t.resolveMatch(find({ cwd: path, root }), root)
+})
+
 t.test('find the git dir at current level', t => {
   const cwd = t.testdir({
     '.git': { index: 'hello' },