diff --git a/package.json b/package.json
index 631b169..08c95ef 100644
--- a/package.json
+++ b/package.json
@@ -24,7 +24,8 @@
     "Titus Wormer <tituswormer@gmail.com> (https://wooorm.com)"
   ],
   "files": [
-    "index.js"
+    "index.js",
+    "types/index.d.ts"
   ],
   "dependencies": {
     "github-slugger": "^1.1.1",
@@ -35,6 +36,7 @@
   },
   "devDependencies": {
     "browserify": "^16.0.0",
+    "dtslint": "^4.0.0",
     "nyc": "^15.0.0",
     "prettier": "^2.0.0",
     "rehype": "^11.0.0",
@@ -42,6 +44,7 @@
     "remark-preset-wooorm": "^7.0.0",
     "tape": "^5.0.0",
     "tinyify": "^2.0.0",
+    "unified": "^9.0.0",
     "xo": "^0.32.0"
   },
   "scripts": {
@@ -51,13 +54,17 @@
     "build": "npm run build-bundle && npm run build-mangle",
     "test-api": "node test",
     "test-coverage": "nyc --reporter lcov tape test.js",
-    "test": "npm run format && npm run build && npm run test-coverage"
+    "test-types": "dtslint types",
+    "test": "npm run format && npm run build && npm run test-coverage && npm run test-types"
   },
   "nyc": {
     "check-coverage": true,
     "lines": 100,
     "functions": 100,
-    "branches": 100
+    "branches": 100,
+    "ignores": [
+      "**/*.ts"
+    ]
   },
   "prettier": {
     "tabWidth": 2,
diff --git a/types/index.d.ts b/types/index.d.ts
new file mode 100644
index 0000000..dd7e876
--- /dev/null
+++ b/types/index.d.ts
@@ -0,0 +1,9 @@
+// Minimum TypeScript Version: 3.0
+import {Plugin} from 'unified'
+
+/**
+ * Add `id`s to headings.
+ */
+declare const slug: Plugin<[]>
+
+export = slug
diff --git a/types/rehype-slug-tests.ts b/types/rehype-slug-tests.ts
new file mode 100644
index 0000000..c019c6b
--- /dev/null
+++ b/types/rehype-slug-tests.ts
@@ -0,0 +1,4 @@
+import unified = require('unified')
+import slug = require('rehype-slug')
+
+unified().use(slug)
diff --git a/types/tsconfig.json b/types/tsconfig.json
new file mode 100644
index 0000000..cc59418
--- /dev/null
+++ b/types/tsconfig.json
@@ -0,0 +1,10 @@
+{
+  "compilerOptions": {
+    "lib": ["es2015"],
+    "strict": true,
+    "baseUrl": ".",
+    "paths": {
+      "rehype-slug": ["index.d.ts"]
+    }
+  }
+}
diff --git a/types/tslint.json b/types/tslint.json
new file mode 100644
index 0000000..70c4494
--- /dev/null
+++ b/types/tslint.json
@@ -0,0 +1,7 @@
+{
+  "extends": "dtslint/dtslint.json",
+  "rules": {
+    "semicolon": false,
+    "whitespace": false
+  }
+}