diff --git a/package.json b/package.json
index 637dae53..bc709274 100644
--- a/package.json
+++ b/package.json
@@ -51,7 +51,7 @@
     "@types/node": "^14.0.11",
     "aegir": "^29.0.1",
     "sinon": "^9.2.0",
-    "typescript": "^3.9.5"
+    "typescript": "^4.1"
   },
   "contributors": [
     "David Dias <daviddias.p@gmail.com>",
@@ -66,7 +66,7 @@
     "Richard Littauer <richard.littauer@gmail.com>",
     "Dmitriy Ryajov <dryajov@gmail.com>",
     "Marcin Rataj <lidel@lidel.org>",
-    "Robert Kiel <robert.kiel@validitylabs.org>",
+    "Robert Kiel <robert.kiel@hoprnet.org>",
     "Maciej Krüger <mkg20001@gmail.com>",
     "Oli Evans <oli@tableflip.io>",
     "Alan Shaw <alan@tableflip.io>",
diff --git a/src/index.d.ts b/src/index.d.ts
index 0fca50e3..ceb22821 100644
--- a/src/index.d.ts
+++ b/src/index.d.ts
@@ -35,7 +35,7 @@ declare interface Protocols {
 declare type NodeAddress = {
   family: "IPv4" | "IPv6";
   address: string;
-  port: string;
+  port: number;
 };
 
 declare type MultiaddrInput = string | Uint8Array | Multiaddr | null;
@@ -95,12 +95,12 @@ declare class Multiaddr {
   /**
    * Returns a tuple of parts
    */
-  tuples(): [number, Uint8Array][];
+  tuples(): [code: number, value: Uint8Array][];
 
   /**
    * Returns a tuple of string/number parts
    */
-  stringTuples(): [number, string | number][];
+  stringTuples(): [code: number, value: string | number][];
 
   /**
    * Encapsulates a Multiaddr in another Multiaddr
@@ -123,7 +123,7 @@ declare class Multiaddr {
   /**
    * Extract the peerId if the multiaddr contains one
    */
-  getPeerId(): string;
+  getPeerId(): string | null;
 
   /**
    * Extract the path if the multiaddr contains one
@@ -156,11 +156,11 @@ declare class Multiaddr {
   /**
    * Resolve multiaddr if containing resolvable hostname.
    */
-  resolve(): Promise<Array<Multiaddr>>
+  resolve(): Promise<Multiaddr[]>
 }
 
 declare namespace Multiaddr {
-  const resolvers: Map < string, (addr: Multiaddr) => Promise < Array < string >>>
+  const resolvers: Map<string, (addr: Multiaddr) => Promise<string[]>>
 
   /**
    * Creates a Multiaddr from a node-friendly address object
diff --git a/src/index.js b/src/index.js
index fc464bd6..9e9d454c 100644
--- a/src/index.js
+++ b/src/index.js
@@ -84,7 +84,16 @@ Multiaddr.prototype.toJSON = Multiaddr.prototype.toString
 Multiaddr.prototype.toOptions = function toOptions () {
   const opts = {}
   const parsed = this.toString().split('/')
-  opts.family = parsed[1] === 'ip4' ? 'ipv4' : 'ipv6'
+  switch (parsed[1]) {
+    case 'ip4':
+      opts.family = 'ipv4'
+      break
+    case 'ip6':
+      opts.family = 'ipv6'
+      break
+    default:
+      throw new Error(`Invalid addr family. Got '${parsed[1]}' instead of 'ip4' or 'ip6'`)
+  }
   opts.host = parsed[2]
   opts.transport = parsed[3]
   opts.port = parseInt(parsed[4])
@@ -462,7 +471,7 @@ Multiaddr.fromNodeAddress = function fromNodeAddress (addr, transport) {
       ip = 'ip6'
       break
     default:
-      throw Error(`Invalid addr family. Got '${addr.family}' instead of 'IPv4' or 'IPv6'`)
+      throw new Error(`Invalid addr family. Got '${addr.family}' instead of 'IPv4' or 'IPv6'`)
   }
   return Multiaddr('/' + [ip, addr.address, transport, addr.port].join('/'))
 }
diff --git a/src/resolvers/dns.d.ts b/src/resolvers/dns.d.ts
new file mode 100644
index 00000000..7f3da17b
--- /dev/null
+++ b/src/resolvers/dns.d.ts
@@ -0,0 +1,7 @@
+// Explains to Typescript that 'dns.js' exports
+// a class that has the same properties as Resolver
+type DNSResolver = typeof import('dns').promises.Resolver
+
+declare var Resolver: DNSResolver
+
+export { Resolver }
\ No newline at end of file
diff --git a/test/index.spec.js b/test/index.spec.js
index c154eb4a..27f9682b 100644
--- a/test/index.spec.js
+++ b/test/index.spec.js
@@ -486,6 +486,9 @@ describe('helpers', () => {
           transport: 'tcp',
           port: 1234
         })
+
+      const errRegex = /Invalid addr family/
+      expect(() => multiaddr('/p2p/QmcgpsyWgH8Y8ajJz1Cu72KnS5uo2Aa2LpzU7kinSupNKC').toOptions()).to.throw(errRegex)
     })
   })
 
@@ -745,7 +748,7 @@ describe('helpers', () => {
         multiaddr.fromNodeAddress({
           address: '192.168.0.1',
           family: 'IPv4',
-          port: '1234'
+          port: 1234
         }, 'tcp').toString()
       ).to.be.eql(
         '/ip4/192.168.0.1/tcp/1234'
diff --git a/test/types.spec.ts b/test/types.spec.ts
index ba9129c9..72ee02e8 100644
--- a/test/types.spec.ts
+++ b/test/types.spec.ts
@@ -12,11 +12,11 @@ export const maFromConstructorFunction: Multiaddr = Multiaddr.fromNodeAddress(
   {
     family: 'IPv4',
     address: '127.0.0.1',
-    port: '12345'
+    port: 12345
   },
   'udp'
 )
 
-export function doSthWithMa (ma: Multiaddr): void {
+export function doSthWithMa(ma: Multiaddr): void {
   ma.toOptions()
 }
diff --git a/tsconfig.json b/tsconfig.json
index 60e2c5b1..7a2adc79 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -1,7 +1,9 @@
 {
   "compilerOptions": {
     "module": "commonjs",
-    "lib": ["es6"],
+    "lib": [
+      "es6"
+    ],
     "target": "ES5",
     "noImplicitAny": false,
     "noImplicitThis": true,
@@ -14,5 +16,9 @@
     "noEmit": true,
     "forceConsistentCasingInFileNames": true
   },
-  "include": ["src/index.d.ts", "test/**/*.spec.js", "test/**/*.spec.ts"]
-}
+  "include": [
+    "src/index.d.ts",
+    "test/**/*.spec.js",
+    "test/**/*.spec.ts"
+  ]
+}
\ No newline at end of file