diff --git a/src/main/index.ts b/src/main/index.ts
index 61ec5487..35699c15 100644
--- a/src/main/index.ts
+++ b/src/main/index.ts
@@ -17,11 +17,12 @@ import StreamingManager from './streaming_manager'
 import Preferences from './preferences'
 import Fonts from './fonts'
 import Hashtags from './hashtags'
-import UnreadNotification from './unread_notification'
+import UnreadNotification from './unreadNotification'
 import i18n from '../config/i18n'
 import Language from '../constants/language'
 import LocalAccount from '~src/types/localAccount'
 import LocalTag from '~src/types/localTag'
+import { UnreadNotification as UnreadNotificationConfig } from '~/src/types/unreadNotification'
 
 /**
  * Context menu
@@ -657,13 +658,13 @@ ipcMain.on('stop-tag-streaming', (_event, _) => {
 })
 
 // sounds
-ipcMain.on('fav-rt-action-sound', (_event, _) => {
+ipcMain.on('fav-rt-action-sound', (_event: Event, _) => {
   const preferences = new Preferences(preferencesDBPath)
   preferences.load()
     .then((conf) => {
       if (conf.general.sound.fav_rb) {
         const sound = path.join(soundBasePath, 'operation_sound01.wav')
-        simplayer(sound, (err) => {
+        simplayer(sound, (err: Error) => {
           if (err) log.error(err)
         })
       }
@@ -671,13 +672,13 @@ ipcMain.on('fav-rt-action-sound', (_event, _) => {
     .catch(err => log.error(err))
 })
 
-ipcMain.on('toot-action-sound', (_event, _) => {
+ipcMain.on('toot-action-sound', (_event: Event, _) => {
   const preferences = new Preferences(preferencesDBPath)
   preferences.load()
     .then((conf) => {
       if (conf.general.sound.toot) {
         const sound = path.join(soundBasePath, 'operation_sound02.wav')
-        simplayer(sound, (err) => {
+        simplayer(sound, (err: Error) => {
           if (err) log.error(err)
         })
       }
@@ -686,7 +687,7 @@ ipcMain.on('toot-action-sound', (_event, _) => {
 })
 
 // preferences
-ipcMain.on('get-preferences', (event, _) => {
+ipcMain.on('get-preferences', (event: Event, _) => {
   const preferences = new Preferences(preferencesDBPath)
   preferences.load()
     .then((conf) => {
@@ -697,7 +698,7 @@ ipcMain.on('get-preferences', (event, _) => {
     })
 })
 
-ipcMain.on('update-preferences', (event, data) => {
+ipcMain.on('update-preferences', (event: Event, data: any) => {
   const preferences = new Preferences(preferencesDBPath)
   preferences.update(data)
     .then((conf) => {
@@ -708,7 +709,7 @@ ipcMain.on('update-preferences', (event, data) => {
     })
 })
 
-ipcMain.on('change-collapse', (_, value) => {
+ipcMain.on('change-collapse', (_, value: boolean) => {
   const preferences = new Preferences(preferencesDBPath)
   preferences.update(
     {
@@ -721,7 +722,7 @@ ipcMain.on('change-collapse', (_, value) => {
     })
 })
 
-ipcMain.on('get-collapse', (event, _) => {
+ipcMain.on('get-collapse', (event: Event, _) => {
   const preferences = new Preferences(preferencesDBPath)
   preferences.load()
     .then((conf) => {
@@ -729,7 +730,7 @@ ipcMain.on('get-collapse', (event, _) => {
     })
 })
 
-ipcMain.on('change-global-header', (event, value) => {
+ipcMain.on('change-global-header', (event: Event, value: boolean) => {
   const preferences = new Preferences(preferencesDBPath)
   preferences.update(
     {
@@ -745,7 +746,7 @@ ipcMain.on('change-global-header', (event, value) => {
     })
 })
 
-ipcMain.on('get-global-header', (event, _) => {
+ipcMain.on('get-global-header', (event: Event, _) => {
   const preferences = new Preferences(preferencesDBPath)
   preferences.load()
     .then((conf) => {
@@ -753,7 +754,7 @@ ipcMain.on('get-global-header', (event, _) => {
     })
 })
 
-ipcMain.on('change-language', (event, value) => {
+ipcMain.on('change-language', (event: Event, value: string) => {
   const preferences = new Preferences(preferencesDBPath)
   preferences.update(
     {
@@ -813,7 +814,7 @@ ipcMain.on('list-fonts', (event: Event, _) => {
 })
 
 // Unread notifications
-ipcMain.on('get-unread-notification', (event, accountID) => {
+ipcMain.on('get-unread-notification', (event: Event, accountID: string) => {
   unreadNotification.findOne({
     accountID: accountID
   })
@@ -826,9 +827,9 @@ ipcMain.on('get-unread-notification', (event, accountID) => {
     })
 })
 
-ipcMain.on('update-unread-notification', (event, obj) => {
-  const { accountID } = obj
-  unreadNotification.insertOrUpdate(accountID, obj)
+ipcMain.on('update-unread-notification', (event: Event, config: UnreadNotificationConfig) => {
+  const { accountID } = config
+  unreadNotification.insertOrUpdate(accountID!, config)
     .then(_ => {
       event.sender.send('response-update-unread-notification', true)
     })
@@ -839,7 +840,7 @@ ipcMain.on('update-unread-notification', (event, obj) => {
 })
 
 // Application control
-ipcMain.on('relaunch', (_event, _) => {
+ipcMain.on('relaunch', (_event: Event, _) => {
   app.relaunch()
   app.exit()
 })
diff --git a/src/main/unread_notification.js b/src/main/unreadNotification.ts
similarity index 74%
rename from src/main/unread_notification.js
rename to src/main/unreadNotification.ts
index 3b61a79d..b2cdc242 100644
--- a/src/main/unread_notification.js
+++ b/src/main/unreadNotification.ts
@@ -1,8 +1,11 @@
 import { isEmpty } from 'lodash'
 import Datastore from 'nedb'
+import { UnreadNotification as Config } from '~/src/types/unreadNotification'
 
 export default class UnreadNotification {
-  constructor (path) {
+  private db: Datastore
+
+  constructor (path: string) {
     this.db = new Datastore({
       filename: path,
       autoload: true
@@ -21,19 +24,19 @@ export default class UnreadNotification {
         // Add unique index.
         this.db.ensureIndex({ fieldName: 'accountID', unique: true, sparse: true }, (err) => {
           if (err) reject(err)
-          resolve(null)
+          resolve({})
         })
       })
     })
   }
 
-  insertOrUpdate (accountID, obj) {
+  insertOrUpdate (accountID: string, config: Config): Promise<number> {
     return new Promise((resolve, reject) => {
       this.db.update(
         {
           accountID: accountID
         },
-        obj,
+        config,
         {
           upsert: true
         },
@@ -44,9 +47,9 @@ export default class UnreadNotification {
     })
   }
 
-  findOne (obj) {
+  findOne (obj: any): Promise<Config> {
     return new Promise((resolve, reject) => {
-      this.db.findOne(obj, (err, doc) => {
+      this.db.findOne<Config>(obj, (err, doc) => {
         if (err) return reject(err)
         if (isEmpty(doc)) return reject(new EmptyRecordError('empty'))
         resolve(doc)
@@ -55,9 +58,4 @@ export default class UnreadNotification {
   }
 }
 
-class EmptyRecordError extends Error {
-  constructor (msg) {
-    super(msg)
-    this.name = 'EmptyRecordError'
-  }
-}
+class EmptyRecordError extends Error {}
diff --git a/src/renderer/store/Settings/Timeline.ts b/src/renderer/store/Settings/Timeline.ts
index bc3f83a6..a9cd1c5a 100644
--- a/src/renderer/store/Settings/Timeline.ts
+++ b/src/renderer/store/Settings/Timeline.ts
@@ -47,8 +47,8 @@ const actions: ActionTree<TimelineState, RootState> = {
       ipcRenderer.send('get-unread-notification', rootState.Settings.accountID)
     })
   },
-  changeUnreadNotification: ({ dispatch, state, rootState }, timeline: object): Promise<boolean> => {
-    const settings = Object.assign({}, state.unreadNotification, timeline, {
+  changeUnreadNotification: ({ dispatch, state, rootState }, timeline: any): Promise<boolean> => {
+    const settings: UnreadNotification = Object.assign({}, state.unreadNotification, timeline, {
       accountID: rootState.Settings.accountID
     })
     return new Promise((resolve, reject) => {
diff --git a/src/types/unreadNotification.ts b/src/types/unreadNotification.ts
index b1861521..8269cf5d 100644
--- a/src/types/unreadNotification.ts
+++ b/src/types/unreadNotification.ts
@@ -1,4 +1,5 @@
 export type UnreadNotification = {
+  accountID?: string,
   direct: boolean,
   local: boolean,
   public: boolean