diff --git a/.prettierrc b/.prettierrc
new file mode 100644
index 0000000..b2095be
--- /dev/null
+++ b/.prettierrc
@@ -0,0 +1,4 @@
+{
+  "semi": false,
+  "singleQuote": true
+}
diff --git a/.vscode/settings.json b/.vscode/settings.json
index 86939ac..593ec7e 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -1,13 +1,14 @@
-// Place your settings in this file to overwrite default and user settings.
 {
-    "files.exclude": {
-        "**/.git": true,
-        "**/.svn": true,
-        "**/.hg": true,
-        "**/CVS": true,
-        "**/.DS_Store": true,
-        "node_modules": true,
-        "coverage": true,
-        "lib": true
-    }
-}
\ No newline at end of file
+  // Place your settings in this file to overwrite default and user settings.
+  "editor.formatOnSave": true,
+  "files.exclude": {
+    "**/.git": true,
+    "**/.svn": true,
+    "**/.hg": true,
+    "**/CVS": true,
+    "**/.DS_Store": true,
+    "node_modules": true,
+    "coverage": true,
+    "lib": true
+  }
+}
diff --git a/package.json b/package.json
index cc44d0c..a07161b 100644
--- a/package.json
+++ b/package.json
@@ -5,10 +5,7 @@
   "engines": {
     "node": ">=6.0.0"
   },
-  "files": [
-    "lib",
-    "bin"
-  ],
+  "files": ["lib", "bin"],
   "bin": {
     "typesync": "./bin/typesync"
   },
@@ -16,16 +13,22 @@
   "scripts": {
     "clean": "rimraf lib",
     "test": "jest",
-    "lint": "tslint 'src/**/*.ts'",
+    "lint": "tslint --fix 'src/**/*.ts' && yarn format",
+    "format": "prettier --write 'src/**/*.ts'",
     "lint:watch": "nodemon --exec npm run lint -e ts,js",
     "cover": "jest --coverage",
     "coveralls": "jest --coverage && cat ./coverage/lcov.info | coveralls",
-    "build": "rimraf lib && tsc -p tsconfig.build.json --sourceMap --declaration",
+    "build":
+      "rimraf lib && tsc -p tsconfig.build.json --sourceMap --declaration",
     "run-cli": "npm run build && node bin/typesync",
-    "do:publish": "npm run lint && npm run cover && npm run build && npm publish",
-    "release:patch": "npm version patch && npm run do:publish && git push --follow-tags",
-    "release:minor": "npm version minor && npm run do:publish && git push --follow-tags",
-    "release:prerelease": "npm version prerelease && npm run do:publish && git push --follow-tags"
+    "do:publish":
+      "npm run lint && npm run cover && npm run build && npm publish",
+    "release:patch":
+      "npm version patch && npm run do:publish && git push --follow-tags",
+    "release:minor":
+      "npm version minor && npm run do:publish && git push --follow-tags",
+    "release:prerelease":
+      "npm version prerelease && npm run do:publish && git push --follow-tags"
   },
   "repository": {
     "type": "git",
@@ -40,16 +43,19 @@
   "devDependencies": {
     "@types/chalk": "^0.4.31",
     "@types/detect-indent": "^5.0.0",
-    "@types/lodash": "^4.14.76",
-    "@types/node": "^8.0.31",
+    "@types/jest": "^21.1.2",
+    "@types/lodash": "^4.14.77",
+    "@types/node": "^8.0.33",
     "@types/ora": "^1.3.1",
     "@types/rimraf": "^2.0.2",
     "coveralls": "^3.0.0",
     "jest": "^21.2.1",
     "nodemon": "^1.12.1",
+    "prettier": "^1.7.4",
     "rimraf": "^2.6.2",
-    "ts-jest": "^21.0.1",
+    "ts-jest": "^21.1.1",
     "tslint": "^5.7.0",
+    "tslint-config-prettier": "^1.5.0",
     "tslint-config-standard": "^6.0.1",
     "typescript": "^2.5.3"
   },
@@ -63,21 +69,13 @@
       "!src/fakes.ts",
       "!src/types.ts"
     ],
-    "coveragePathIgnorePatterns": [
-      "/node_modules/"
-    ],
+    "coveragePathIgnorePatterns": ["/node_modules/"],
     "transform": {
       ".(ts|tsx)": "<rootDir>/node_modules/ts-jest/preprocessor.js"
     },
     "testRegex": "(/__tests__/.*\\.(test|spec))\\.(ts|tsx|js)$",
-    "testPathIgnorePatterns": [
-      "/lib/"
-    ],
-    "moduleFileExtensions": [
-      "ts",
-      "tsx",
-      "js"
-    ]
+    "testPathIgnorePatterns": ["/lib/"],
+    "moduleFileExtensions": ["ts", "tsx", "js"]
   },
   "dependencies": {
     "awilix": "^2.8.1",
diff --git a/src/__tests__/package-json-file-service.test.ts b/src/__tests__/package-json-file-service.test.ts
index 1034769..8309cbe 100644
--- a/src/__tests__/package-json-file-service.test.ts
+++ b/src/__tests__/package-json-file-service.test.ts
@@ -19,8 +19,9 @@ describe('package json file service', () => {
 
     it('throws when file does not exist', async () => {
       expect.assertions(1)
-      await subject.readPackageFile('nonexistent.json')
-        .catch((err) => expect(err.message).toMatch(/exist/i))
+      await subject
+        .readPackageFile('nonexistent.json')
+        .catch(err => expect(err.message).toMatch(/exist/i))
     })
   })
 
@@ -76,18 +77,23 @@ describe('package json file service', () => {
   })
 })
 
-function _writeFixture (withTrailingNewline = false): Promise<string> {
+function _writeFixture(withTrailingNewline = false): Promise<string> {
   const file = path.join(os.tmpdir(), `package-${Math.random()}.json`)
-  return writeFileAsync(file, JSON.stringify({
-    name: 'fony-package',
-    dependencies: {
-      package1: '^1.0.0'
-    }
-  }, null, 2) + (withTrailingNewline ? '\n' : '')).then(() => file)
+  return writeFileAsync(
+    file,
+    JSON.stringify(
+      {
+        name: 'fony-package',
+        dependencies: {
+          package1: '^1.0.0'
+        }
+      },
+      null,
+      2
+    ) + (withTrailingNewline ? '\n' : '')
+  ).then(() => file)
 }
 
-function cleanup (...files: string[]): Promise<any> {
-  return Promise.all(
-    files.map(f => unlinkAsync(f))
-  )
+function cleanup(...files: string[]): Promise<any> {
+  return Promise.all(files.map(f => unlinkAsync(f)))
 }
diff --git a/src/__tests__/type-syncer.test.ts b/src/__tests__/type-syncer.test.ts
index 2e22e51..5e5dbc0 100644
--- a/src/__tests__/type-syncer.test.ts
+++ b/src/__tests__/type-syncer.test.ts
@@ -7,19 +7,29 @@ import {
 } from '../types'
 import { createTypeSyncer } from '../type-syncer'
 
-const typedefs: ITypeDefinition[] = [{
-  typingsName: 'package1'
-}, {
-  typingsName: 'package2'
-}, {
-  typingsName: 'package3'
-}, {
-  typingsName: 'package4'
-}, {
-  typingsName: 'package5'
-}]
+const typedefs: ITypeDefinition[] = [
+  {
+    typingsName: 'package1'
+  },
+  {
+    typingsName: 'package2'
+  },
+  {
+    typingsName: 'package3'
+  },
+  {
+    typingsName: 'package4'
+  },
+  {
+    typingsName: 'package5'
+  },
+  // None for package6
+  {
+    typingsName: 'myorg__package7'
+  }
+]
 
-function buildSyncer () {
+function buildSyncer() {
   const typedefSource: ITypeDefinitionSource = {
     fetch: jest.fn(() => Promise.resolve(typedefs)),
     getLatestTypingsVersion: jest.fn(() => Promise.resolve('1.0.0'))
@@ -38,6 +48,12 @@ function buildSyncer () {
       '@types/package4': '^1.0.0',
       package4: '^1.0.0',
       package5: '^1.0.0'
+    },
+    optionalDependencies: {
+      package6: '^1.0.0'
+    },
+    peerDependencies: {
+      '@myorg/package7': '^1.0.0'
     }
   }
 
@@ -45,10 +61,7 @@ function buildSyncer () {
     typedefSource,
     packageService,
     packageFile,
-    syncer: createTypeSyncer(
-      packageService,
-      typedefSource
-    )
+    syncer: createTypeSyncer(packageService, typedefSource)
   }
 }
 
@@ -56,21 +69,28 @@ describe('type syncer', () => {
   it('adds new packages to the package.json', async () => {
     const { syncer, packageService, typedefSource } = buildSyncer()
     const result = await syncer.sync('package.json')
-    const writtenPackage = (packageService.writePackageFile as jest.Mock<any>).mock.calls[0][1] as IPackageFile
+    const writtenPackage = (packageService.writePackageFile as jest.Mock<any>)
+      .mock.calls[0][1] as IPackageFile
     expect(writtenPackage.devDependencies).toEqual({
       '@types/package1': '^1.0.0',
       '@types/package3': '^1.0.0',
       '@types/package4': '^1.0.0',
       '@types/package5': '^1.0.0',
+      '@types/myorg__package7': '^1.0.0',
       package4: '^1.0.0',
       package5: '^1.0.0'
     })
-    expect(result.newTypings.map(x => x.typingsName).sort()).toEqual(['package1', 'package3', 'package5'])
+    expect(result.newTypings.map(x => x.typingsName).sort()).toEqual([
+      'myorg__package7',
+      'package1',
+      'package3',
+      'package5'
+    ])
   })
 
   it('does not write packages if options.dry is specified', async () => {
     const { syncer, packageService, typedefSource } = buildSyncer()
     const result = await syncer.sync('package.json', { dry: true })
-    expect((packageService.writePackageFile as jest.Mock<any>)).not.toBeCalled()
+    expect(packageService.writePackageFile as jest.Mock<any>).not.toBeCalled()
   })
 })
diff --git a/src/__tests__/util.test.ts b/src/__tests__/util.test.ts
index 51b7b15..4e7f8ac 100644
--- a/src/__tests__/util.test.ts
+++ b/src/__tests__/util.test.ts
@@ -9,18 +9,19 @@ describe('util', () => {
 
   describe('filterMap', () => {
     it('filters out false values', () => {
-      expect(filterMap(
-        [1, 2, 3, 4],
-        (item) => item % 2 === 0 ? false : item + 1
-      )).toEqual([2, 4])
+      expect(
+        filterMap([1, 2, 3, 4], item => (item % 2 === 0 ? false : item + 1))
+      ).toEqual([2, 4])
     })
   })
 
   describe('mergeObjects', () => {
     it('merges an array of objects', () => {
-      expect(mergeObjects(
-        [{ a: 1 }, { b: 2 }, { a: 3 }, { c: 4 }]
-      )).toEqual({ a: 3, b: 2, c: 4 })
+      expect(mergeObjects([{ a: 1 }, { b: 2 }, { a: 3 }, { c: 4 }])).toEqual({
+        a: 3,
+        b: 2,
+        c: 4
+      })
     })
   })
 
@@ -36,7 +37,8 @@ describe('util', () => {
 
   describe('promisify', () => {
     it('resolves when the callback is successful', async () => {
-      const original = (arg1: any, arg2: any, cb: Function) => cb(null, arg1 + arg2)
+      const original = (arg1: any, arg2: any, cb: Function) =>
+        cb(null, arg1 + arg2)
       const promisified = promisify(original)
       const result = await promisified(2, 2)
       expect(result).toBe(4)
@@ -50,14 +52,16 @@ describe('util', () => {
     })
 
     it('rejects when the callback is not successful', async () => {
-      const original = (arg1: any, arg2: any, cb: Function) => cb(new Error('oh shit'), null)
+      const original = (arg1: any, arg2: any, cb: Function) =>
+        cb(new Error('oh shit'), null)
       const promisified = promisify(original)
       const err = await promisified(2, 2).catch(err => err)
       expect(err.message).toBe('oh shit')
     })
 
     it('rejects when the callback is not successful even if only passed 1 param', async () => {
-      const original = (arg1: any, arg2: any, cb: Function) => cb(new Error('oh shit'))
+      const original = (arg1: any, arg2: any, cb: Function) =>
+        cb(new Error('oh shit'))
       const promisified = promisify(original)
       const err = await promisified(2, 2).catch(err => err)
       expect(err.message).toBe('oh shit')
diff --git a/src/cli-util.ts b/src/cli-util.ts
index cd78928..57e80b4 100644
--- a/src/cli-util.ts
+++ b/src/cli-util.ts
@@ -7,7 +7,7 @@ const ora = require('ora')
  * Like regular console.log, but better.
  * @param message
  */
-export function log (message: string) {
+export function log(message: string) {
   console.log(`${chalk.white('»')}  ${chalk.gray(message)}`)
 }
 
@@ -15,7 +15,7 @@ export function log (message: string) {
  * Makes success feel even sweeter.
  * @param text
  */
-export function success (text: string) {
+export function success(text: string) {
   console.log(`${chalk.green('✔')}  ${chalk.white(text)}`)
 }
 
@@ -23,7 +23,7 @@ export function success (text: string) {
  * Logs an error all pretty.
  * @param err
  */
-export function error (err: Error | string) {
+export function error(err: Error | string) {
   const msg = err instanceof Error ? err.message : err
   const stack = err instanceof Error ? `\nStack:\n${err.stack}` : ''
   console.log(`${chalk.red('✖')}  ${chalk.bgRed(chalk.white(msg))}${stack}`)
@@ -34,7 +34,7 @@ export function error (err: Error | string) {
  * @param text
  * @param fn
  */
-export async function spinWhile<T> (text: string, fn: () => Promise<T>) {
+export async function spinWhile<T>(text: string, fn: () => Promise<T>) {
   const spinner = ora(' ' + chalk.gray(text)).start()
   try {
     return await fn()
@@ -47,7 +47,7 @@ export async function spinWhile<T> (text: string, fn: () => Promise<T>) {
  * Super simple argument parser.
  * @param argv
  */
-export function parseArguments (argv: Array<string>): ICLIArguments {
+export function parseArguments(argv: Array<string>): ICLIArguments {
   const flags: { [key: string]: boolean } = {}
   const args: Array<string> = []
   for (const arg of argv) {
diff --git a/src/cli.ts b/src/cli.ts
index 3536cda..036d6a9 100644
--- a/src/cli.ts
+++ b/src/cli.ts
@@ -12,7 +12,7 @@ import { createPackageJSONFileService } from './package-json-file-service'
 /**
  * Starts the TypeSync CLI.
  */
-export async function startCli () {
+export async function startCli() {
   try {
     // Awilix is a dependency injection container.
     const container = createContainer({
@@ -29,7 +29,7 @@ export async function startCli () {
   }
 }
 
-async function _runCli (syncer: ITypeSyncer) {
+async function _runCli(syncer: ITypeSyncer) {
   const { args, flags } = parseArguments(process.argv.slice(2))
   const [filePath = 'package.json'] = args
   if (flags.help) {
@@ -50,20 +50,25 @@ async function _runCli (syncer: ITypeSyncer) {
   C.success(
     result.newTypings.length === 0
       ? `No new typings added, looks like you're all synced up!`
-      : (chalk as any)`${result.newTypings.length} typings added:\n${formattedTypings}\n\n✨  Go ahead and run {green npm install} or {green yarn} to install the packages that were added.`
+      : (chalk as any)`${result.newTypings
+          .length} typings added:\n${formattedTypings}\n\n✨  Go ahead and run {green npm install} or {green yarn} to install the packages that were added.`
   )
 }
 
-function formatPackageName (t: ITypeDefinition) {
-  return `${chalk.bold.green('+')}  ${chalk.gray('@types/')}${chalk.bold.blue(t.typingsName)}`
+function formatPackageName(t: ITypeDefinition) {
+  return `${chalk.bold.green('+')}  ${chalk.gray('@types/')}${chalk.bold.blue(
+    t.typingsName
+  )}`
 }
 
-function printHelp () {
-  console.log((chalk as any)`
+function printHelp() {
+  console.log(
+    (chalk as any)`
 {blue.bold typesync} - adds missing TypeScript definitions to package.json
 
 Options
   {magenta.bold --dry}      dry run, won't save the package.json
   {magenta.bold --help}     shows this help menu
-  `.trim())
+  `.trim()
+  )
 }
diff --git a/src/fakes.ts b/src/fakes.ts
index 83c3f0c..02831c2 100644
--- a/src/fakes.ts
+++ b/src/fakes.ts
@@ -5,17 +5,23 @@ import {
   IPackageFile
 } from './types'
 
-const typedefs: ITypeDefinition[] = [{
-  typingsName: 'package1'
-}, {
-  typingsName: 'package2'
-}, {
-  typingsName: 'packagethree'
-}, {
-  typingsName: 'package4'
-}, {
-  typingsName: 'package5'
-}]
+const typedefs: ITypeDefinition[] = [
+  {
+    typingsName: 'package1'
+  },
+  {
+    typingsName: 'package2'
+  },
+  {
+    typingsName: 'packagethree'
+  },
+  {
+    typingsName: 'package4'
+  },
+  {
+    typingsName: 'package5'
+  }
+]
 
 const packageFile: IPackageFile = {
   name: 'consumer',
@@ -30,18 +36,18 @@ const packageFile: IPackageFile = {
   }
 }
 
-function delay (ms: number): Promise<void> {
-  return new Promise<void>((resolve) => setTimeout(resolve, ms))
+function delay(ms: number): Promise<void> {
+  return new Promise<void>(resolve => setTimeout(resolve, ms))
 }
 
-export function fakePackageService (): IPackageJSONService {
+export function fakePackageService(): IPackageJSONService {
   return {
     readPackageFile: () => delay(10).then(() => packageFile),
     writePackageFile: () => delay(10)
   }
 }
 
-export function fakeTypeDefSource (): ITypeDefinitionSource {
+export function fakeTypeDefSource(): ITypeDefinitionSource {
   return {
     fetch: () => delay(4000).then(() => typedefs),
     getLatestTypingsVersion: () => delay(600).then(() => '1.0.0')
diff --git a/src/package-json-file-service.ts b/src/package-json-file-service.ts
index b12c2bc..bc64788 100644
--- a/src/package-json-file-service.ts
+++ b/src/package-json-file-service.ts
@@ -7,9 +7,9 @@ const existsAsync = promisify(fs.exists)
 const readFileAsync = promisify(fs.readFile)
 const writeFileAsync = promisify(fs.writeFile)
 
-export function createPackageJSONFileService (): IPackageJSONService {
+export function createPackageJSONFileService(): IPackageJSONService {
   return {
-    readPackageFile: async (filePath) => {
+    readPackageFile: async filePath => {
       const contents = await readFileContents(filePath)
       return JSON.parse(contents) as IPackageFile
     },
@@ -19,18 +19,22 @@ export function createPackageJSONFileService (): IPackageJSONService {
       const trailingNewline = contents.length
         ? contents[contents.length - 1] === '\n'
         : false
-      const data = JSON.stringify(fileContent, null, indent /* istanbul ignore next */ || '  ')
+      const data = JSON.stringify(
+        fileContent,
+        null,
+        indent /* istanbul ignore next */ || '  '
+      )
       await writeFileAsync(filePath, data + (trailingNewline ? '\n' : ''))
     }
   }
 }
 
-async function readFileContents (filePath: string) {
+async function readFileContents(filePath: string) {
   await assertFile(filePath)
   return readFileAsync(filePath, 'utf-8').then((x: Buffer) => x.toString())
 }
 
-async function assertFile (filePath: string) {
+async function assertFile(filePath: string) {
   if (!await existsAsync(filePath)) {
     throw new Error(`${filePath} does not exist.`)
   }
diff --git a/src/type-definition-source.ts b/src/type-definition-source.ts
index 75693d4..2b5c22d 100644
--- a/src/type-definition-source.ts
+++ b/src/type-definition-source.ts
@@ -3,7 +3,8 @@ import axios, { AxiosResponse } from 'axios'
 import { typed } from './util'
 import * as zlip from 'zlib'
 
-const typedefsUrl = 'https://typespublisher.blob.core.windows.net/typespublisher/data/search-index-min.json'
+const typedefsUrl =
+  'https://typespublisher.blob.core.windows.net/typespublisher/data/search-index-min.json'
 
 const npmClient = axios.create({
   baseURL: 'https://registry.npmjs.org'
@@ -12,7 +13,7 @@ const npmClient = axios.create({
 /**
  * Used to pull definitions.
  */
-export function createTypeDefinitionSource (): ITypeDefinitionSource {
+export function createTypeDefinitionSource(): ITypeDefinitionSource {
   return {
     /**
      * Fetches available type defs.
@@ -44,7 +45,7 @@ export function createTypeDefinitionSource (): ITypeDefinitionSource {
  * Unzips a gzip-encoded response.
  * @param response
  */
-function unzipResponse (response: AxiosResponse) {
+function unzipResponse(response: AxiosResponse) {
   return new Promise<Array<any>>(resolve => {
     const unzip = zlip.createGunzip()
     let json = ''
diff --git a/src/type-syncer.ts b/src/type-syncer.ts
index 473bc8c..4568314 100644
--- a/src/type-syncer.ts
+++ b/src/type-syncer.ts
@@ -15,7 +15,7 @@ import { uniq, filterMap, mergeObjects, typed, orderObject } from './util'
  * @param packageJSONservice
  * @param typeDefinitionSource
  */
-export function createTypeSyncer (
+export function createTypeSyncer(
   packageJSONService: IPackageJSONService,
   typeDefinitionSource: ITypeDefinitionSource
 ): ITypeSyncer {
@@ -30,18 +30,29 @@ export function createTypeSyncer (
       ])
 
       const allPackageNames = uniq([
-        ...file.dependencies && Object.keys(file.dependencies) /* istanbul ignore next*/ || [],
-        ...file.devDependencies && Object.keys(file.devDependencies) /* istanbul ignore next*/ || []
+        ...((file.dependencies &&
+          Object.keys(file.dependencies)) /* istanbul ignore next*/ ||
+          []),
+        ...((file.devDependencies &&
+          Object.keys(file.devDependencies)) /* istanbul ignore next*/ ||
+          []),
+        ...((file.optionalDependencies &&
+          Object.keys(file.optionalDependencies)) /* istanbul ignore next*/ ||
+          []),
+        ...((file.peerDependencies &&
+          Object.keys(file.peerDependencies)) /* istanbul ignore next*/ ||
+          [])
       ])
 
       const newTypings = filterNewTypings(allPackageNames, allTypings)
       const devDepsToAdd = await Promise.all(
         newTypings.map(async t => {
-          const latestVersion = await typeDefinitionSource.getLatestTypingsVersion(t.typingsName)
+          const latestVersion = await typeDefinitionSource.getLatestTypingsVersion(
+            t.typingsName
+          )
           return { [typed(t.typingsName)]: `^${latestVersion}` }
         })
-      )
-        .then(mergeObjects)
+      ).then(mergeObjects)
 
       if (!opts.dry) {
         await packageJSONService.writePackageFile(filePath, {
@@ -66,12 +77,17 @@ export function createTypeSyncer (
  * @param allPackageNames Used to filter the typings that are new.
  * @param allTypings All typings available
  */
-function filterNewTypings (
+function filterNewTypings(
   allPackageNames: Array<string>,
   allTypings: Array<ITypeDefinition>
 ): Array<ITypeDefinition> {
   const existingTypings = allPackageNames.filter(x => x.startsWith('@types/'))
   return filterMap(allPackageNames, p => {
+    const scopeInfo = getPackageScope(p)
+    if (scopeInfo && scopeInfo[0] !== 'types') {
+      p = `${scopeInfo[0]}__${scopeInfo[1]}`
+    }
+
     const typingsForPackage = allTypings.find(x => x.typingsName === p)
     if (!typingsForPackage) {
       // No typings available.
@@ -87,3 +103,18 @@ function filterNewTypings (
     return typingsForPackage
   })
 }
+
+/**
+ * If a package is scoped, returns the scope + package as a tuple, otherwise null.
+ *
+ * @param packageName Package name to check scope for.
+ */
+function getPackageScope(packageName: string): [string, string] | null {
+  const EXPR = /^\@([^\/]+)\/(.*)$/i
+  const matches = EXPR.exec(packageName)
+  if (!matches) {
+    return null
+  }
+
+  return [matches[1], matches[2]]
+}
diff --git a/src/types.ts b/src/types.ts
index 4eedf76..ff1cf69 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -2,7 +2,7 @@
  * The guts of the program.
  */
 export interface ITypeSyncer {
-  sync (filePath: string, opts?: ISyncOptions): Promise<ISyncResult>
+  sync(filePath: string, opts?: ISyncOptions): Promise<ISyncResult>
 }
 
 /**
@@ -22,11 +22,11 @@ export interface ITypeDefinitionSource {
   /**
    * Fetches available type definitions.
    */
-  fetch (): Promise<Array<ITypeDefinition>>
+  fetch(): Promise<Array<ITypeDefinition>>
   /**
    * Gets the latest version of the typings for the specified typings package.
    */
-  getLatestTypingsVersion (typingsPackageName: string): Promise<string>
+  getLatestTypingsVersion(typingsPackageName: string): Promise<string>
 }
 
 /**
@@ -36,11 +36,11 @@ export interface IPackageJSONService {
   /**
    * Reads and parses JSON from the specified file. Path is relative to the current working directory.
    */
-  readPackageFile (filePath: string): Promise<IPackageFile>
+  readPackageFile(filePath: string): Promise<IPackageFile>
   /**
    * Writes the JSON to the specified file.
    */
-  writePackageFile (filePath: string, fileContents: IPackageFile): Promise<void>
+  writePackageFile(filePath: string, fileContents: IPackageFile): Promise<void>
 }
 
 /**
@@ -50,6 +50,8 @@ export interface IPackageFile {
   name: string
   dependencies?: IDependenciesSection
   devDependencies?: IDependenciesSection
+  peerDependencies?: IDependenciesSection
+  optionalDependencies?: IDependenciesSection
   [key: string]: any
 }
 
diff --git a/src/util.ts b/src/util.ts
index 05230f6..e40fe81 100644
--- a/src/util.ts
+++ b/src/util.ts
@@ -3,7 +3,7 @@
  *
  * @param source The source to filter
  */
-export function uniq<T> (source: Array<T>): Array<T> {
+export function uniq<T>(source: Array<T>): Array<T> {
   const seen: T[] = []
   for (const s of source) {
     if (seen.includes(s)) {
@@ -21,7 +21,7 @@ export function uniq<T> (source: Array<T>): Array<T> {
  * @param source The source to filter and map
  * @param iteratee The iteratee.
  */
-export function filterMap <T, R> (
+export function filterMap<T, R>(
   source: Array<T>,
   iteratee: (item: T, index: number) => R | false
 ): Array<R> {
@@ -41,7 +41,7 @@ export function filterMap <T, R> (
  *
  * @param source An array of objects to merge.
  */
-export function mergeObjects<T> (source: Array<T>): T {
+export function mergeObjects<T>(source: Array<T>): T {
   return source.reduce((accum: any, next: any) => ({ ...accum, ...next }), {})
 }
 
@@ -49,7 +49,7 @@ export function mergeObjects<T> (source: Array<T>): T {
  * Returns the assumed types package name.
  * @param name Package name
  */
-export function typed (name: string, urlEncode = false): string {
+export function typed(name: string, urlEncode = false): string {
   return `@types${urlEncode ? '%2F' : '/'}${name}`
 }
 
@@ -57,7 +57,7 @@ export function typed (name: string, urlEncode = false): string {
  * Orders an object.
  * @param source
  */
-export function orderObject<T> (source: T): T {
+export function orderObject<T>(source: T): T {
   const keys = Object.keys(source).sort()
   const result: any = {}
   for (const key of keys) {
@@ -72,10 +72,10 @@ export function orderObject<T> (source: T): T {
  *
  * @param fn
  */
-export function promisify (fn: Function) {
-  return function promisified (...args: any[]) {
+export function promisify(fn: Function) {
+  return function promisified(...args: any[]) {
     return new Promise<any>((resolve, reject) => {
-      fn(...args, function callback (err: any, result: any) {
+      fn(...args, function callback(err: any, result: any) {
         // Edge case with `fs.exists`.
         if (arguments.length === 1 && typeof err === 'boolean') {
           return resolve(err)
diff --git a/tslint.json b/tslint.json
index 4569837..fdc792b 100644
--- a/tslint.json
+++ b/tslint.json
@@ -1,6 +1,7 @@
 {
   "extends": [
-    "tslint-config-standard"
+    "tslint-config-standard",
+    "tslint-config-prettier"
   ],
   "rules": {
     "semicolon": [
@@ -8,7 +9,7 @@
       "never"
     ],
     "quotemark": [
-      "single"
+      true, "single"
     ],
     "no-var-requires": false,
     "trailing-comma": [false],
diff --git a/yarn.lock b/yarn.lock
index 6919e8e..af1d07e 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -17,13 +17,13 @@
     "@types/minimatch" "*"
     "@types/node" "*"
 
-"@types/jest@^21.1.1":
-  version "21.1.1"
-  resolved "https://registry.yarnpkg.com/@types/jest/-/jest-21.1.1.tgz#70008ecce439774a45c7d0b543d879ec58a1b332"
+"@types/jest@^21.1.2":
+  version "21.1.2"
+  resolved "https://registry.yarnpkg.com/@types/jest/-/jest-21.1.2.tgz#05ebfa64817b626694ced56745a7949281981048"
 
-"@types/lodash@^4.14.76":
-  version "4.14.76"
-  resolved "https://registry.yarnpkg.com/@types/lodash/-/lodash-4.14.76.tgz#87874f766774d54e89589697340be9496fb8bf70"
+"@types/lodash@^4.14.77":
+  version "4.14.77"
+  resolved "https://registry.yarnpkg.com/@types/lodash/-/lodash-4.14.77.tgz#0bc699413e84d6ed5d927ca30ea0f0a890b42d75"
 
 "@types/minimatch@*":
   version "3.0.1"
@@ -33,9 +33,9 @@
   version "8.0.10"
   resolved "https://registry.yarnpkg.com/@types/node/-/node-8.0.10.tgz#12efec9183b072d5f951cf86395a4c780f868a17"
 
-"@types/node@^8.0.31":
-  version "8.0.31"
-  resolved "https://registry.yarnpkg.com/@types/node/-/node-8.0.31.tgz#d9af61093cf4bfc9f066ca34de0175012cfb0ce9"
+"@types/node@^8.0.33":
+  version "8.0.33"
+  resolved "https://registry.yarnpkg.com/@types/node/-/node-8.0.33.tgz#1126e94374014e54478092830704f6ea89df04cd"
 
 "@types/ora@^1.3.1":
   version "1.3.1"
@@ -326,7 +326,7 @@ babel-plugin-transform-strict-mode@^6.24.1:
     babel-runtime "^6.22.0"
     babel-types "^6.24.1"
 
-babel-preset-jest@^21.0.0, babel-preset-jest@^21.2.0:
+babel-preset-jest@^21.2.0:
   version "21.2.0"
   resolved "https://registry.yarnpkg.com/babel-preset-jest/-/babel-preset-jest-21.2.0.tgz#ff9d2bce08abd98e8a36d9a8a5189b9173b85638"
   dependencies:
@@ -1491,7 +1491,7 @@ jest-cli@^21.2.1:
     worker-farm "^1.3.1"
     yargs "^9.0.0"
 
-jest-config@^21.0.0, jest-config@^21.2.1:
+jest-config@^21.2.1:
   version "21.2.1"
   resolved "https://registry.yarnpkg.com/jest-config/-/jest-config-21.2.1.tgz#c7586c79ead0bcc1f38c401e55f964f13bf2a480"
   dependencies:
@@ -1649,7 +1649,7 @@ jest-snapshot@^21.2.1:
     natural-compare "^1.4.0"
     pretty-format "^21.2.1"
 
-jest-util@^21.0.0, jest-util@^21.2.1:
+jest-util@^21.2.1:
   version "21.2.1"
   resolved "https://registry.yarnpkg.com/jest-util/-/jest-util-21.2.1.tgz#a274b2f726b0897494d694a6c3d6a61ab819bb78"
   dependencies:
@@ -2335,6 +2335,10 @@ preserve@^0.2.0:
   version "0.2.0"
   resolved "https://registry.yarnpkg.com/preserve/-/preserve-0.2.0.tgz#815ed1f6ebc65926f865b310c0713bcb3315ce4b"
 
+prettier@^1.7.4:
+  version "1.7.4"
+  resolved "https://registry.yarnpkg.com/prettier/-/prettier-1.7.4.tgz#5e8624ae9363c80f95ec644584ecdf55d74f93fa"
+
 pretty-format@^21.2.1:
   version "21.2.1"
   resolved "https://registry.yarnpkg.com/pretty-format/-/pretty-format-21.2.1.tgz#ae5407f3cf21066cd011aa1ba5fce7b6a2eddb36"
@@ -2652,12 +2656,18 @@ sntp@1.x.x:
   dependencies:
     hoek "2.x.x"
 
-source-map-support@^0.4.2, source-map-support@^0.4.4:
+source-map-support@^0.4.2:
   version "0.4.15"
   resolved "https://registry.yarnpkg.com/source-map-support/-/source-map-support-0.4.15.tgz#03202df65c06d2bd8c7ec2362a193056fef8d3b1"
   dependencies:
     source-map "^0.5.6"
 
+source-map-support@^0.5.0:
+  version "0.5.0"
+  resolved "https://registry.yarnpkg.com/source-map-support/-/source-map-support-0.5.0.tgz#2018a7ad2bdf8faf2691e5fddab26bed5a2bacab"
+  dependencies:
+    source-map "^0.6.0"
+
 source-map@^0.4.4:
   version "0.4.4"
   resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.4.4.tgz#eba4f5da9c0dc999de68032d8b4f76173652036b"
@@ -2668,6 +2678,10 @@ source-map@^0.5.0, source-map@^0.5.3, source-map@^0.5.6, source-map@~0.5.1:
   version "0.5.6"
   resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.5.6.tgz#75ce38f52bf0733c5a7f0c118d81334a2bb5f412"
 
+source-map@^0.6.0:
+  version "0.6.1"
+  resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.6.1.tgz#74722af32e9614e9c287a8d0bbde48b5e2f1a263"
+
 source-map@~0.2.0:
   version "0.2.0"
   resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.2.0.tgz#dab73fbcfc2ba819b4de03bd6f6eaa48164b3f9d"
@@ -2877,25 +2891,29 @@ trim-right@^1.0.1:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/trim-right/-/trim-right-1.0.1.tgz#cb2e1203067e0c8de1f614094b9fe45704ea6003"
 
-ts-jest@^21.0.1:
-  version "21.0.1"
-  resolved "https://registry.yarnpkg.com/ts-jest/-/ts-jest-21.0.1.tgz#825138413eb299d12d60d0ae4d5a49f76b1cfeac"
+ts-jest@^21.1.1:
+  version "21.1.1"
+  resolved "https://registry.yarnpkg.com/ts-jest/-/ts-jest-21.1.1.tgz#a63380127e59e112a113106237f302d17c72cd48"
   dependencies:
     babel-core "^6.24.1"
     babel-plugin-istanbul "^4.1.4"
     babel-plugin-transform-es2015-modules-commonjs "^6.24.1"
-    babel-preset-jest "^21.0.0"
+    babel-preset-jest "^21.2.0"
     fs-extra "^4.0.0"
-    jest-config "^21.0.0"
-    jest-util "^21.0.0"
+    jest-config "^21.2.1"
+    jest-util "^21.2.1"
     pkg-dir "^2.0.0"
-    source-map-support "^0.4.4"
-    yargs "^8.0.1"
+    source-map-support "^0.5.0"
+    yargs "^9.0.1"
 
 tslib@^1.0.0, tslib@^1.7.1:
   version "1.7.1"
   resolved "https://registry.yarnpkg.com/tslib/-/tslib-1.7.1.tgz#bc8004164691923a79fe8378bbeb3da2017538ec"
 
+tslint-config-prettier@^1.5.0:
+  version "1.5.0"
+  resolved "https://registry.yarnpkg.com/tslint-config-prettier/-/tslint-config-prettier-1.5.0.tgz#76645425edcc34d9b6835ba58266eaf90fdbfeda"
+
 tslint-config-standard@^6.0.1:
   version "6.0.1"
   resolved "https://registry.yarnpkg.com/tslint-config-standard/-/tslint-config-standard-6.0.1.tgz#a04ba0a794759e877287056f549b081e47a56d6c"
@@ -3162,25 +3180,7 @@ yargs-parser@^7.0.0:
   dependencies:
     camelcase "^4.1.0"
 
-yargs@^8.0.1:
-  version "8.0.2"
-  resolved "https://registry.yarnpkg.com/yargs/-/yargs-8.0.2.tgz#6299a9055b1cefc969ff7e79c1d918dceb22c360"
-  dependencies:
-    camelcase "^4.1.0"
-    cliui "^3.2.0"
-    decamelize "^1.1.1"
-    get-caller-file "^1.0.1"
-    os-locale "^2.0.0"
-    read-pkg-up "^2.0.0"
-    require-directory "^2.1.1"
-    require-main-filename "^1.0.1"
-    set-blocking "^2.0.0"
-    string-width "^2.0.0"
-    which-module "^2.0.0"
-    y18n "^3.2.1"
-    yargs-parser "^7.0.0"
-
-yargs@^9.0.0:
+yargs@^9.0.0, yargs@^9.0.1:
   version "9.0.1"
   resolved "https://registry.yarnpkg.com/yargs/-/yargs-9.0.1.tgz#52acc23feecac34042078ee78c0c007f5085db4c"
   dependencies: