diff --git a/lib/history.ts b/lib/history.ts
index 6c3919ea0..d193234e0 100644
--- a/lib/history.ts
+++ b/lib/history.ts
@@ -1,4 +1,3 @@
-'use strict'
 // history
 // external modules
 import LZString from 'lz-string'
diff --git a/lib/letter-avatars.ts b/lib/letter-avatars.ts
index 2f9a27118..3d038047b 100644
--- a/lib/letter-avatars.ts
+++ b/lib/letter-avatars.ts
@@ -1,4 +1,3 @@
-'use strict'
 import { createHash } from 'crypto'
 import randomColor from 'randomcolor'
 import { config } from './config'
diff --git a/lib/logger.ts b/lib/logger.ts
index ee084df23..8711bbd1b 100644
--- a/lib/logger.ts
+++ b/lib/logger.ts
@@ -1,4 +1,3 @@
-'use strict'
 import { createLogger, format, transports } from 'winston'
 
 const logger = createLogger({
diff --git a/lib/response.ts b/lib/response.ts
index 498402fdf..f1a0739ed 100644
--- a/lib/response.ts
+++ b/lib/response.ts
@@ -1,4 +1,3 @@
-'use strict'
 import { config } from './config'
 import { Note, User } from './models'
 
diff --git a/lib/web/utils.ts b/lib/web/utils.ts
index 1a8454462..6da5ceb99 100644
--- a/lib/web/utils.ts
+++ b/lib/web/utils.ts
@@ -1,5 +1,3 @@
-'use strict'
-
 import bodyParser from 'body-parser'
 // create application/x-www-form-urlencoded parser