diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 34306ef..21e55ce 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node-version: [14.0.0, 16, 18]
+        node-version: [16.0.0, 18, 20]
     steps:
       - uses: actions/checkout@v3
       - name: Use Node.js ${{ matrix.node-version }}
diff --git a/lib/doctest.js b/lib/doctest.js
index a8d7dc8..79125d7 100644
--- a/lib/doctest.js
+++ b/lib/doctest.js
@@ -8,9 +8,9 @@
 ///     >>>>>>>>   >>>>>>>    >>>>>>>    >>>>   >>>>>>>    >>>>>>    >>>>
 ///    .....................x.......xx.x.................................
 
-import fs from 'fs/promises';
-import {dirname, resolve} from 'path';
-import vm from 'vm';
+import fs from 'node:fs/promises';
+import {dirname, resolve} from 'node:path';
+import vm from 'node:vm';
 
 import * as acorn from 'acorn';
 import CoffeeScript from 'coffeescript';
diff --git a/lib/require.js b/lib/require.js
index b2129f4..857608d 100644
--- a/lib/require.js
+++ b/lib/require.js
@@ -1,4 +1,4 @@
-import module from 'module';
-import url from 'url';
+import module from 'node:module';
+import url from 'node:url';
 
 export default module.createRequire (url.fileURLToPath (import.meta.url));
diff --git a/package.json b/package.json
index 22d4ac2..52ec0ff 100644
--- a/package.json
+++ b/package.json
@@ -20,7 +20,7 @@
     "url": "git://github.com/davidchambers/doctest.git"
   },
   "engines": {
-    "node": ">=14.0.0"
+    "node": ">=16.0.0"
   },
   "dependencies": {
     "acorn": "8.11.x",
diff --git a/test/esm/dependencies.js b/test/esm/dependencies.js
index dbed67c..a7397d8 100644
--- a/test/esm/dependencies.js
+++ b/test/esm/dependencies.js
@@ -1,6 +1,6 @@
 // Convert degrees Celsius to degrees Fahrenheit.
 //
-// > import util from 'util'
+// > import util from 'node:util'
 // > util.inspect (toFahrenheit (0))
 // '32'
 export function toFahrenheit(degreesCelsius) {
diff --git a/test/index.js b/test/index.js
index 1e48987..9af2cef 100644
--- a/test/index.js
+++ b/test/index.js
@@ -1,6 +1,6 @@
-import {strictEqual} from 'assert';
-import {exec} from 'child_process';
-import {promisify} from 'util';
+import {strictEqual} from 'node:assert';
+import {exec} from 'node:child_process';
+import {promisify} from 'node:util';
 
 import test from 'oletus';
 import show from 'sanctuary-show';