diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index f174caa..67a9ae5 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -4,6 +4,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - uses: ./.github/actions/prepare
+      - run: pnpm build
       - run: pnpm lint
 
 name: Lint
diff --git a/.github/workflows/test-cjs.yml b/.github/workflows/test-cjs.yml
new file mode 100644
index 0000000..9348c04
--- /dev/null
+++ b/.github/workflows/test-cjs.yml
@@ -0,0 +1,16 @@
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: ./.github/actions/prepare
+      - run: pnpm build
+      - run: pnpm run test:cjs
+
+name: Test CommonJS
+
+on:
+  pull_request: ~
+  push:
+    branches:
+      - main
diff --git a/package.json b/package.json
index 9b89c9c..8bf5815 100644
--- a/package.json
+++ b/package.json
@@ -29,6 +29,10 @@
   "type": "module",
   "exports": {
     ".": {
+      "types": {
+        "import": "./lib/index.d.ts",
+        "require": "./lib/index.d.cts"
+      },
       "import": "./lib/index.js",
       "require": "./lib/index.cjs"
     }
@@ -52,14 +56,15 @@
     "prepare": "husky install",
     "should-semantic-release": "should-semantic-release --verbose",
     "test": "vitest",
+    "test:cjs": "node ./src/e2e.cjs",
     "tsc": "tsc"
   },
   "lint-staged": {
     "*": "prettier --ignore-unknown --write"
   },
   "dependencies": {
-    "@sindresorhus/is": "^6.0.0",
-    "char-regex": "^2.0.0",
+    "@sindresorhus/is": "^4.6.0",
+    "char-regex": "^1.0.2",
     "emojilib": "^2.4.0",
     "skin-tone": "^2.0.0"
   },
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 39497b3..1aa128b 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -6,11 +6,11 @@ settings:
 
 dependencies:
   '@sindresorhus/is':
-    specifier: ^6.0.0
-    version: 6.0.0
+    specifier: ^4.6.0
+    version: 4.6.0
   char-regex:
-    specifier: ^2.0.0
-    version: 2.0.1
+    specifier: ^1.0.2
+    version: 1.0.2
   emojilib:
     specifier: ^2.4.0
     version: 2.4.0
@@ -1434,16 +1434,16 @@ packages:
     resolution: {integrity: sha512-+Fj43pSMwJs4KRrH/938Uf+uAELIgVBmQzg/q1YG10djyfA3TnrU8N8XzqCh/okZdszqBQTZf96idMfE5lnwTA==}
     dev: true
 
+  /@sindresorhus/is@4.6.0:
+    resolution: {integrity: sha512-t09vSN3MdfsyCHoFcTRCH/iUtG7OJ0CsjzB8cjAmKc/va/kIgeDI/TxsigdncE/4be734m0cvIYwNaV4i2XqAw==}
+    engines: {node: '>=10'}
+    dev: false
+
   /@sindresorhus/is@5.3.0:
     resolution: {integrity: sha512-CX6t4SYQ37lzxicAqsBtxA3OseeoVrh9cSJ5PFYam0GksYlupRfy1A+Q4aYD3zvcfECLc0zO2u+ZnR2UYKvCrw==}
     engines: {node: '>=14.16'}
     dev: true
 
-  /@sindresorhus/is@6.0.0:
-    resolution: {integrity: sha512-iVkg+3V+GJfof7yAHOxHyoiEfgpRJhnddOY3EsTM/uqwcm6M/jDQwK1n1nnraMpTRT36CxS0RCtJohggaQ0jgQ==}
-    engines: {node: '>=16'}
-    dev: false
-
   /@sindresorhus/merge-streams@1.0.0:
     resolution: {integrity: sha512-rUV5WyJrJLoloD4NDN1V1+LDMDWOa4OTsT4yYJwQNpTU6FWxkxHpL7eu4w+DmiH8x/EAM1otkPE1+LaspIbplw==}
     engines: {node: '>=18'}
@@ -2313,9 +2313,9 @@ packages:
     engines: {node: ^12.17.0 || ^14.13 || >=16.0.0}
     dev: true
 
-  /char-regex@2.0.1:
-    resolution: {integrity: sha512-oSvEeo6ZUD7NepqAat3RqoucZ5SeqLJgOvVIwkafu6IP3V0pO38s/ypdVUmDDK6qIIHNlYHJAKX9E7R7HoKElw==}
-    engines: {node: '>=12.20'}
+  /char-regex@1.0.2:
+    resolution: {integrity: sha512-kWWXztvZ5SBQV+eRgKFeh8q5sLuZY2+8WUIzlxWVTg+oGwY14qylx1KbKzHd8P6ZYkAg0xyIDU9JMHhyJMZ1jw==}
+    engines: {node: '>=10'}
     dev: false
 
   /character-entities-legacy@1.1.4:
diff --git a/src/e2e.cjs b/src/e2e.cjs
new file mode 100644
index 0000000..e35c73f
--- /dev/null
+++ b/src/e2e.cjs
@@ -0,0 +1,5 @@
+const { strict: assert } = require('node:assert')
+
+const emoji = require('../lib/index.cjs')
+
+assert.equal(emoji.emojify(':wave:'), '👋')
diff --git a/src/emojify.ts b/src/emojify.ts
index d21107d..e1d41eb 100644
--- a/src/emojify.ts
+++ b/src/emojify.ts
@@ -1,4 +1,4 @@
-import { assert, default as is } from '@sindresorhus/is'
+import is from '@sindresorhus/is'
 
 import { findByName } from './findByName.js'
 import { asFunction, normalizeName } from './utils.js'
@@ -21,9 +21,9 @@ export const emojify = (
   const fallbackFunction =
     fallback === undefined ? fallback : asFunction(fallback)
 
-  assert.string(input)
-  assert.any([is.undefined, is.function], fallbackFunction)
-  assert.function(format)
+  is.assert.string(input)
+  is.assert.any([is.default.undefined, is.default.function_], fallbackFunction)
+  is.assert.function_(format)
 
   return input.replace(/:[\w\-+]+:/g, part => {
     const found = findByName(part)
diff --git a/src/replace.ts b/src/replace.ts
index 663258b..5ea5966 100644
--- a/src/replace.ts
+++ b/src/replace.ts
@@ -18,7 +18,7 @@ export const replace = (
   const replace = asFunction(replacement)
 
   assert.string(input)
-  assert.function(replace)
+  assert.function_(replace)
   assert.boolean(preserveSpaces)
 
   const characters = input.match(charRegexMatcher)
diff --git a/vitest.config.ts b/vitest.config.ts
index d209a18..6a43cb1 100644
--- a/vitest.config.ts
+++ b/vitest.config.ts
@@ -6,7 +6,7 @@ export default defineConfig({
     coverage: {
       all: true,
       branches: 100,
-      exclude: ['lib', 'src/*.d.ts', 'src/index.ts'],
+      exclude: ['lib', 'src/*.d.ts', 'src/e2e.cjs', 'src/index.ts'],
       functions: 100,
       include: ['src'],
       lines: 100,