diff --git a/.github/workflows/node.js.yml b/.github/workflows/node.js.yml
index f4ed5a0..9120d3f 100644
--- a/.github/workflows/node.js.yml
+++ b/.github/workflows/node.js.yml
@@ -17,7 +17,7 @@ jobs:
         node-version: 20.x
 
     - name: Install tools
-      run: npm install --location=global bslint
+      run: npm install --location=global bslint typescript
 
     - name: Install dependencies
       run: npm install
@@ -25,6 +25,9 @@ jobs:
     - name: Lint
       run: npm run lint
 
+    - name: Lint types
+      run: npm run lint-types
+
   cover:
     name: Coverage test
     runs-on: ubuntu-latest
diff --git a/lib/ip.js b/lib/ip.js
index 3845f34..0afc82e 100644
--- a/lib/ip.js
+++ b/lib/ip.js
@@ -29,6 +29,10 @@ const inet = require('./inet');
 const onion = require('./onion');
 const binet = exports;
 
+/** @typedef {import('bufio').BufferWriter} BufferWriter */
+/** @typedef {import('bufio').StaticWriter} StaticWriter */
+/** @typedef {import('bufio').BufferReader} BufferReader */
+
 /*
  * Constants
  */
@@ -225,19 +229,21 @@ binet.write = function write(dst, str, off, size) {
 
 /**
  * Write an IP string to a buffer writer.
- * @param {BufferWriter} bw
+ * @param {BufferWriter|StaticWriter} bw
  * @param {String} str
  * @param {Number} [size=16]
- * @returns {BufferWriter}
+ * @returns {BufferWriter|StaticWriter}
  */
 
 binet.writeBW = function writeBW(bw, str, size) {
   assert(bw && typeof bw === 'object');
 
   // StaticWriter
+  // @ts-ignore
   if (bw.data) {
-    bw.offset = binet.write(bw.data, str, bw.offset, size);
-    return bw;
+    const sw = /** @type {StaticWriter} */(bw);
+    sw.offset = binet.write(sw.data, str, sw.offset, size);
+    return sw;
   }
 
   const buf = Buffer.alloc(size);
@@ -696,7 +702,7 @@ binet.isEqualString = function isEqualString(a, b) {
  * Apply a network mask to IP.
  * @param {String} str
  * @param {String} mask
- * @returns {Buffer}
+ * @returns {String}
  */
 
 binet.maskString = function maskString(str, mask) {
@@ -715,7 +721,7 @@ binet.maskString = function maskString(str, mask) {
  * to IP from CIDR bits.
  * @param {String} str
  * @param {Number} bits
- * @returns {Buffer}
+ * @returns {String}
  */
 
 binet.cidrString = function cidrString(str, bits) {
@@ -1382,7 +1388,7 @@ binet.getReachability = function getReachability(src, dest) {
  * @private
  * @param {Number} filter
  * @param {Number} af
- * @returns {String}
+ * @returns {String[]}
  */
 
 binet._interfaces = function _interfaces(filter, af) {
@@ -1472,7 +1478,7 @@ binet._interfaces = function _interfaces(filter, af) {
 /**
  * Get local IP from network interfaces.
  * @param {String?} family - IP family name.
- * @returns {String}
+ * @returns {String[]}
  */
 
 binet.getInterfaces = function getInterfaces(family) {
@@ -1482,7 +1488,7 @@ binet.getInterfaces = function getInterfaces(family) {
 /**
  * Get local IP from network interfaces.
  * @param {String?} family - IP family name.
- * @returns {String}
+ * @returns {String[]}
  */
 
 binet.getLocal = function getLocal(family) {
@@ -1492,7 +1498,7 @@ binet.getLocal = function getLocal(family) {
 /**
  * Get non-local IP from network interfaces.
  * @param {String?} family - IP family name.
- * @returns {String}
+ * @returns {String[]}
  */
 
 binet.getNonlocal = function getNonlocal(family) {
@@ -1502,7 +1508,7 @@ binet.getNonlocal = function getNonlocal(family) {
 /**
  * Get private IP from network interfaces.
  * @param {String?} family - IP family name.
- * @returns {String}
+ * @returns {String[]}
  */
 
 binet.getPrivate = function getPrivate(family) {
@@ -1512,7 +1518,7 @@ binet.getPrivate = function getPrivate(family) {
 /**
  * Get public IP from network interfaces.
  * @param {String?} family - IP family name.
- * @returns {String}
+ * @returns {String[]}
  */
 
 binet.getPublic = function getPublic(family) {
@@ -1588,9 +1594,13 @@ binet.equal = binet.isEqualString;
  * Compat (deprecated)
  */
 
+// @ts-ignore
 types.NAME = 0;
+// @ts-ignore
 types.DNS = 0;
+// @ts-ignore
 types.IPV4 = 4;
+// @ts-ignore
 types.IPV6 = 6;
 
 binet.toString = binet.encode;
diff --git a/lib/onion.js b/lib/onion.js
index 41e9c0b..76d5d49 100644
--- a/lib/onion.js
+++ b/lib/onion.js
@@ -39,7 +39,7 @@ onion.is = function is(raw) {
 
 /**
  * Encode onion address.
- * @param {Buffer} key
+ * @param {Buffer} raw
  * @param {Function} sha3
  * @returns {String}
  */
@@ -116,7 +116,7 @@ onion.isLegacy = function isLegacy(raw) {
 
 /**
  * Encode onion address.
- * @param {Buffer} key
+ * @param {Buffer} raw
  * @returns {String}
  */
 
diff --git a/package-lock.json b/package-lock.json
index 6285210..7b3fe61 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -9,12 +9,13 @@
       "version": "0.3.7",
       "license": "MIT",
       "dependencies": {
-        "bs32": "~0.1.5",
-        "bsert": "~0.0.10"
+        "bs32": "https://github.com/nodech/bs32#ts-lint",
+        "bsert": "~0.0.12"
       },
       "devDependencies": {
-        "bmocha": "^2.1.0",
-        "bufio": "^1.0.7"
+        "bmocha": "^2.1.8",
+        "bts-type-deps": "^0.0.3",
+        "bufio": "https://github.com/nodech/bufio#ts-lint"
       },
       "engines": {
         "node": ">=8.0.0"
@@ -35,8 +36,8 @@
     },
     "node_modules/bs32": {
       "version": "0.1.6",
-      "resolved": "https://registry.npmjs.org/bs32/-/bs32-0.1.6.tgz",
-      "integrity": "sha512-usjDesQqZ8ihHXOnOEQuAdymBHnJEfSd+aELFSg1jN/V3iAf12HrylHlRJwIt6DTMmXpBDQ+YBg3Q3DIYdhRgQ==",
+      "resolved": "git+ssh://git@github.com/nodech/bs32.git#6a625986ddf8f8290298f1970226bce76f6c389e",
+      "license": "MIT",
       "dependencies": {
         "bsert": "~0.0.10"
       },
@@ -52,13 +53,19 @@
         "node": ">=8.0.0"
       }
     },
+    "node_modules/bts-type-deps": {
+      "version": "0.0.3",
+      "resolved": "https://registry.npmjs.org/bts-type-deps/-/bts-type-deps-0.0.3.tgz",
+      "integrity": "sha512-OQHGWhX5amae6Vj6ShlGaQu0sNCICgJ5YspNZPRzfR5RobrD+wjm5vkZK/J3EH5b/ymxqSWo9VkiFNpCxjaG2Q==",
+      "dev": true
+    },
     "node_modules/bufio": {
       "version": "1.2.0",
-      "resolved": "https://registry.npmjs.org/bufio/-/bufio-1.2.0.tgz",
-      "integrity": "sha512-UlFk8z/PwdhYQTXSQQagwGAdtRI83gib2n4uy4rQnenxUM2yQi8lBDzF230BNk+3wAoZDxYRoBwVVUPgHa9MCA==",
+      "resolved": "git+ssh://git@github.com/nodech/bufio.git#59135453e7ca5190df32f216239e2c18a019f5bc",
       "dev": true,
+      "license": "MIT",
       "engines": {
-        "node": ">=8.0.0"
+        "node": ">=14.0.0"
       }
     }
   }
diff --git a/package.json b/package.json
index 30c9801..a91af55 100644
--- a/package.json
+++ b/package.json
@@ -18,16 +18,18 @@
   "main": "./lib/binet.js",
   "scripts": {
     "lint": "eslint lib/ test/",
+    "lint-types": "tsc -p .",
     "test": "bmocha --reporter spec test/*-test.js",
     "test-ci": "nyc --reporter lcov bmocha -- --reporter spec test/*.js"
   },
   "dependencies": {
     "bs32": "~0.1.5",
-    "bsert": "~0.0.10"
+    "bsert": "~0.0.12"
   },
   "devDependencies": {
-    "bmocha": "^2.1.0",
-    "bufio": "^1.0.7"
+    "bmocha": "^2.1.8",
+    "bts-type-deps": "^0.0.3",
+    "bufio": "^1.2.0"
   },
   "engines": {
     "node": ">=8.0.0"
diff --git a/tsconfig.json b/tsconfig.json
new file mode 100644
index 0000000..56c78ac
--- /dev/null
+++ b/tsconfig.json
@@ -0,0 +1,31 @@
+{
+  "include": [
+    "lib/**/*.js"
+  ],
+  "compilerOptions": {
+    "rootDir": ".",
+    "target": "ES2016",
+    "lib": [
+      "ES2016"
+    ],
+
+    "noEmit": true,
+
+    "allowJs": true,
+    "checkJs": true,
+    "maxNodeModuleJsDepth": 2,
+
+    "module": "commonjs",
+    "moduleResolution": "node",
+    "resolveJsonModule": true,
+
+    "stripInternal": true,
+    "noImplicitThis": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": false,
+
+    "typeRoots": [
+      "node_modules/bts-type-deps/types"
+    ]
+  }
+}