diff --git a/README.md b/README.md
index 325581c..6dde25a 100644
--- a/README.md
+++ b/README.md
@@ -213,18 +213,21 @@ unflatten({
 
 ```sh
 npx flat foo.json
+npx flat --unflatten foo.json
 ```
 
 Or install the `flat` command globally:
  
 ```sh
 npm i -g flat && flat foo.json
+npm i -g flat && flat --unflatten foo.json
 ```
 
 Accepts a filename as an argument:
 
 ```sh
 flat foo.json
+flat --unflatten foo.json
 ```
 
 Also accepts JSON on stdin:
diff --git a/cli.js b/cli.js
index a1efc3f..e241086 100755
--- a/cli.js
+++ b/cli.js
@@ -2,9 +2,12 @@
 import fs from 'node:fs'
 import path from 'node:path'
 import readline from 'node:readline'
-import { flatten } from './index.js'
+import { flatten, unflatten } from './index.js'
+
+const args = process.argv.slice(2)
+const shouldUnflatten = args.includes('--unflatten')
+const filepath = args.find(arg => !arg.startsWith('--'))
 
-const filepath = process.argv.slice(2)[0]
 if (filepath) {
   // Read from file
   const file = path.resolve(process.cwd(), filepath)
@@ -25,15 +28,16 @@ if (filepath) {
 }
 
 function out (data) {
-  process.stdout.write(JSON.stringify(flatten(data), null, 2))
+  const transformed = shouldUnflatten ? unflatten(data) : flatten(data)
+  process.stdout.write(JSON.stringify(transformed, null, 2))
 }
 
 function usage (code) {
   console.log(`
 Usage:
 
-flat foo.json
-cat foo.json | flat
+flat [--unflatten] foo.json
+cat foo.json | flat [--unflatten]
 `)
 
   process.exit(code || 0)