diff --git a/examples/client_auto/client_auto.js b/examples/client_auto/client_auto.js
index fdc586d..e89e803 100644
--- a/examples/client_auto/client_auto.js
+++ b/examples/client_auto/client_auto.js
@@ -1,3 +1,5 @@
+'use strict';
+
 var mc = require('minecraft-protocol');
 
 if(process.argv.length < 4 || process.argv.length > 6) {
diff --git a/src/browser.js b/src/browser.js
index 3e2d3ea..13195f9 100644
--- a/src/browser.js
+++ b/src/browser.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Client = require('./client');
 const Server = require('./server');
 const serializer = require("./transforms/serializer");
diff --git a/src/client.js b/src/client.js
index addae5d..bec22c4 100644
--- a/src/client.js
+++ b/src/client.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const EventEmitter = require('events').EventEmitter;
 const debug = require('debug')('minecraft-protocol');
 const compression = require('./transforms/compression');
diff --git a/src/client/autoVersion.js b/src/client/autoVersion.js
index 2123948..9cc4cbd 100644
--- a/src/client/autoVersion.js
+++ b/src/client/autoVersion.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const ping = require('../ping');
 const debug = require('debug')('minecraft-protocol');
 const states = require('../states');
diff --git a/src/client/encrypt.js b/src/client/encrypt.js
index 81cff81..510526d 100644
--- a/src/client/encrypt.js
+++ b/src/client/encrypt.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const crypto = require('crypto');
 const yggserver = require('yggdrasil').server({});
 const ursa=require("../ursa");
diff --git a/src/client/keepalive.js b/src/client/keepalive.js
index 0eab56e..17f212f 100644
--- a/src/client/keepalive.js
+++ b/src/client/keepalive.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports = function(client, options) {
   const keepAlive = options.keepAlive == null ? true : options.keepAlive;
   if (!keepAlive) return;
diff --git a/src/client/setProtocol.js b/src/client/setProtocol.js
index 727f4ad..3eb572f 100644
--- a/src/client/setProtocol.js
+++ b/src/client/setProtocol.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const states = require("../states");
 
 module.exports = function(client, options) {
diff --git a/src/createClient.js b/src/createClient.js
index ee5ab96..6601d24 100644
--- a/src/createClient.js
+++ b/src/createClient.js
@@ -1,7 +1,8 @@
+'use strict';
+
 const Client = require('./client');
 const assert = require('assert');
 
-
 const encrypt = require('./client/encrypt');
 const keepalive = require('./client/keepalive');
 const compress = require('./client/compress');
diff --git a/src/createServer.js b/src/createServer.js
index c805d43..9e8978a 100644
--- a/src/createServer.js
+++ b/src/createServer.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const ursa=require("./ursa");
 const crypto = require('crypto');
 const yggserver = require('yggdrasil').server({});
diff --git a/src/datatypes/minecraft.js b/src/datatypes/minecraft.js
index aee358e..325cf10 100644
--- a/src/datatypes/minecraft.js
+++ b/src/datatypes/minecraft.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const nbt = require('prismarine-nbt');
 const UUID = require('uuid-1345');
 const zlib = require('zlib');
diff --git a/src/index.js b/src/index.js
index 024ae3e..e806dcd 100644
--- a/src/index.js
+++ b/src/index.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const Client = require('./client');
 const Server = require('./server');
 const serializer = require("./transforms/serializer");
diff --git a/src/ping.js b/src/ping.js
index 5ec3ab7..50232aa 100644
--- a/src/ping.js
+++ b/src/ping.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const net = require('net');
 const Client = require('./client');
 const states = require("./states");
diff --git a/src/server.js b/src/server.js
index fb96fa2..da4ec4b 100644
--- a/src/server.js
+++ b/src/server.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const net = require('net');
 const EventEmitter = require('events').EventEmitter;
 const Client = require('./client');
diff --git a/src/states.js b/src/states.js
index 56f4de5..ca9260f 100644
--- a/src/states.js
+++ b/src/states.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const states = {
   "HANDSHAKING": "handshaking",
   "STATUS": "status",
diff --git a/src/transforms/compression.js b/src/transforms/compression.js
index 8275033..2778d0f 100644
--- a/src/transforms/compression.js
+++ b/src/transforms/compression.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const [readVarInt, writeVarInt, sizeOfVarInt] = require("protodef").types.varint;
 const zlib = require("zlib");
 const Transform = require("readable-stream").Transform;
diff --git a/src/transforms/framing.js b/src/transforms/framing.js
index 5f96648..42687ac 100644
--- a/src/transforms/framing.js
+++ b/src/transforms/framing.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const [readVarInt, writeVarInt, sizeOfVarInt] = require("protodef").types.varint;
 const Transform = require("readable-stream").Transform;
 
diff --git a/src/transforms/serializer.js b/src/transforms/serializer.js
index 7756451..d5dcafa 100644
--- a/src/transforms/serializer.js
+++ b/src/transforms/serializer.js
@@ -1,3 +1,5 @@
+'use strict';
+
 const ProtoDef = require("protodef").ProtoDef;
 const Serializer = require("protodef").Serializer;
 const Parser = require("protodef").Parser;
diff --git a/src/ursa.js b/src/ursa.js
index 1ca32d5..c478df6 100644
--- a/src/ursa.js
+++ b/src/ursa.js
@@ -1,3 +1,5 @@
+'use strict';
+
 let ursa;
 try {
   ursa = require("ursa");
diff --git a/src/version.js b/src/version.js
index ea5964c..de52e4e 100644
--- a/src/version.js
+++ b/src/version.js
@@ -1,3 +1,5 @@
+'use strict';
+
 module.exports={
   defaultVersion:'1.8',
   supportedVersions:['1.7','1.8','15w40b','1.9']