diff --git a/HISTORY.md b/HISTORY.md
index 6806136c..503eb3d6 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -23,6 +23,7 @@ unreleased
     - deps: mime-types@~2.1.1
     - perf: reduce try block size
     - perf: remove bitwise operations
+  * perf: enable strict mode
   * perf: remove argument reassignment
 
 1.12.4 / 2015-05-10
diff --git a/index.js b/index.js
index cb4c78a7..b071de99 100644
--- a/index.js
+++ b/index.js
@@ -4,6 +4,8 @@
  * MIT Licensed
  */
 
+'use strict'
+
 /**
  * Module dependencies.
  * @private
diff --git a/lib/read.js b/lib/read.js
index 47ea88f9..e37ce344 100644
--- a/lib/read.js
+++ b/lib/read.js
@@ -4,6 +4,8 @@
  * MIT Licensed
  */
 
+'use strict'
+
 /**
  * Module dependencies.
  */
diff --git a/lib/types/json.js b/lib/types/json.js
index 668df3af..4a0a7546 100644
--- a/lib/types/json.js
+++ b/lib/types/json.js
@@ -5,6 +5,8 @@
  * MIT Licensed
  */
 
+'use strict'
+
 /**
  * Module dependencies.
  */
diff --git a/lib/types/raw.js b/lib/types/raw.js
index 6843c6d7..519146ca 100644
--- a/lib/types/raw.js
+++ b/lib/types/raw.js
@@ -4,6 +4,8 @@
  * MIT Licensed
  */
 
+'use strict'
+
 /**
  * Module dependencies.
  */
diff --git a/lib/types/text.js b/lib/types/text.js
index f558c3b4..caf79684 100644
--- a/lib/types/text.js
+++ b/lib/types/text.js
@@ -4,6 +4,8 @@
  * MIT Licensed
  */
 
+'use strict'
+
 /**
  * Module dependencies.
  */
diff --git a/lib/types/urlencoded.js b/lib/types/urlencoded.js
index 71091eff..bc65947e 100644
--- a/lib/types/urlencoded.js
+++ b/lib/types/urlencoded.js
@@ -5,6 +5,8 @@
  * MIT Licensed
  */
 
+'use strict'
+
 /**
  * Module dependencies.
  */