diff --git a/package.json b/package.json
index 89eb2d6..0088a52 100644
--- a/package.json
+++ b/package.json
@@ -10,7 +10,15 @@
   "repository": "https://github.com/mike-marcacci/node-redlock.git",
   "homepage": "https://github.com/mike-marcacci/node-redlock#readme",
   "bugs": "https://github.com/mike-marcacci/node-redlock/issues",
-  "main": "dist/index.js",
+  "main": "./dist/cjs/index.js",
+  "module": "./dist/esm/index.js",
+  "types": "./dist/index.d.ts",
+  "exports": {
+    ".": {
+      "import": "./dist/esm/index.js",
+      "require": "./dist/cjs/index.js"
+    }
+  },
   "keywords": [
     "nodejs",
     "redlock",
@@ -20,8 +28,10 @@
   ],
   "files": [
     "dist/index.d.ts",
-    "dist/index.js",
-    "dist/index.js.map"
+    "dist/esm/index.js",
+    "dist/esm/index.js.map",
+    "dist/cjs/index.js",
+    "dist/cjs/index.js.map"
   ],
   "engines": {
     "node": ">=12"
@@ -49,10 +59,10 @@
   "scripts": {
     "format": "prettier --list-different --write '**/*.{json,yml,md,ts}'",
     "lint": "prettier -c '**/*.{json,yml,md,ts}' && eslint src --ext ts",
-    "build": "rm -rf dist && tsc",
+    "build": "rm -rf dist && tsc && tsc -p tsconfig.cjs.json && ./tools/fixup",
     "build:development": "rm -rf dist && tsc --watch",
-    "test": "ava --verbose dist/*.test.js",
-    "test:development": "ava --verbose --watch dist/*.test.js",
+    "test": "cd dist/esm && ava --verbose *.test.js",
+    "test:development": "cd dist/esm && ava --verbose --watch *.test.js",
     "prepare": "yarn build",
     "prepublishOnly": "yarn install && yarn lint && yarn build"
   },
diff --git a/tools/fixup b/tools/fixup
new file mode 100755
index 0000000..5a45407
--- /dev/null
+++ b/tools/fixup
@@ -0,0 +1,16 @@
+#!/bin/bash
+#
+#   Add package.json files to cjs/esm subtrees
+#
+
+cat >dist/cjs/package.json <<!EOF
+{
+    "type": "commonjs"
+}
+!EOF
+
+cat >dist/esm/package.json <<!EOF
+{
+    "type": "module"
+}
+!EOF
diff --git a/tsconfig.cjs.json b/tsconfig.cjs.json
new file mode 100644
index 0000000..b604f2e
--- /dev/null
+++ b/tsconfig.cjs.json
@@ -0,0 +1,9 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "declarationDir": null,
+    "declaration": false,
+    "module": "commonjs",
+    "outDir": "./dist/cjs"
+  }
+}
diff --git a/tsconfig.json b/tsconfig.json
index f5ec5ab..32566b5 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -3,7 +3,7 @@
     "lib": ["es2020"],
     "target": "es2018",
     "module": "es2020",
-    "outDir": "./dist",
+    "outDir": "./dist/esm",
     "declaration": true,
     "declarationDir": "./dist",
     "moduleResolution": "node",