diff --git a/lib/collection.js b/lib/collection.js
index 1e92f16e..ec7aaac9 100644
--- a/lib/collection.js
+++ b/lib/collection.js
@@ -1,6 +1,7 @@
 /*
  * Module dependencies.
  */
+'use strict'
 
 var util = require('./util')
 var debug = require('debug')('monk:queries')
diff --git a/lib/helpers.js b/lib/helpers.js
index bfc66c12..0c6c1a0d 100644
--- a/lib/helpers.js
+++ b/lib/helpers.js
@@ -1,3 +1,5 @@
+'use strict'
+
 var ObjectId = require('mongodb').ObjectID
 
 /**
diff --git a/lib/manager.js b/lib/manager.js
index dfe61255..632842ad 100644
--- a/lib/manager.js
+++ b/lib/manager.js
@@ -1,6 +1,7 @@
 /*
  * Module dependencies.
  */
+'use strict'
 
 var mongo = require('mongodb')
 var Debug = require('debug')
diff --git a/lib/monk.js b/lib/monk.js
index 10c3d9ff..de88ed4f 100644
--- a/lib/monk.js
+++ b/lib/monk.js
@@ -1,7 +1,7 @@
-
 /*
  * Module exports
  */
+'use strict'
 
 module.exports = exports = require('./manager')
 
diff --git a/lib/util.js b/lib/util.js
index 24831369..c56b9784 100755
--- a/lib/util.js
+++ b/lib/util.js
@@ -1,3 +1,5 @@
+'use strict'
+
 var id = require('./helpers').id
 
 /**