diff --git a/api/schema.js b/api/schema.js
index c161378..fbeba56 100644
--- a/api/schema.js
+++ b/api/schema.js
@@ -1,3 +1,5 @@
+'use strict'
+
 const { GraphQLSchema } = require('graphql')
 const { MutationType } = require('./types/Mutation')
 const { QueryType } = require('./types/Query')
diff --git a/api/server.js b/api/server.js
index 658a731..e3c5a32 100644
--- a/api/server.js
+++ b/api/server.js
@@ -1,3 +1,5 @@
+'use strict'
+
 const { createWriteStream, unlink } = require('fs')
 const { ApolloServer } = require('apollo-server-koa')
 const Koa = require('koa')
diff --git a/api/types/File.js b/api/types/File.js
index b8e5cef..7ecd0b6 100644
--- a/api/types/File.js
+++ b/api/types/File.js
@@ -1,3 +1,5 @@
+'use strict'
+
 const {
   GraphQLNonNull,
   GraphQLObjectType,
diff --git a/api/types/Mutation.js b/api/types/Mutation.js
index 52921b8..38266e9 100644
--- a/api/types/Mutation.js
+++ b/api/types/Mutation.js
@@ -1,3 +1,5 @@
+'use strict'
+
 const { GraphQLUpload } = require('apollo-server-koa')
 const { GraphQLList, GraphQLObjectType, GraphQLNonNull } = require('graphql')
 const promisesAll = require('promises-all')
diff --git a/api/types/Query.js b/api/types/Query.js
index c7a895f..78d4497 100644
--- a/api/types/Query.js
+++ b/api/types/Query.js
@@ -1,3 +1,5 @@
+'use strict'
+
 const { GraphQLList, GraphQLObjectType, GraphQLNonNull } = require('graphql')
 const { FileType } = require('./File')