diff --git a/common/content/abbreviations.js b/common/content/abbreviations.js
index 28a900d4..f2171090 100644
--- a/common/content/abbreviations.js
+++ b/common/content/abbreviations.js
@@ -4,7 +4,7 @@
 //
 // This work is licensed for reuse under an MIT license. Details are
 // given in the LICENSE.txt file included with this file.
-
+"use strict";
 
 /** @scope modules */
 
diff --git a/melodactyl/content/config.js b/melodactyl/content/config.js
index 01f2a432..21594d57 100644
--- a/melodactyl/content/config.js
+++ b/melodactyl/content/config.js
@@ -4,7 +4,7 @@
 //
 // This work is licensed for reuse under an MIT license. Details are
 // given in the LICENSE.txt file included with this file.
-
+"use strict";
 
 Components.utils.import("resource://gre/modules/utils.js"); // XXX
 
diff --git a/melodactyl/content/library.js b/melodactyl/content/library.js
index bd626461..30f1dfe1 100644
--- a/melodactyl/content/library.js
+++ b/melodactyl/content/library.js
@@ -3,7 +3,7 @@
 //
 // This work is licensed for reuse under an MIT license. Details are
 // given in the LICENSE.txt file included with this file.
-
+"use strict";
 
 // TODO: flesh this out
 const Library = Module("library", {
diff --git a/melodactyl/content/player.js b/melodactyl/content/player.js
index 1d223fde..1d04f904 100644
--- a/melodactyl/content/player.js
+++ b/melodactyl/content/player.js
@@ -3,7 +3,7 @@
 //
 // This work is licensed for reuse under an MIT license. Details are
 // given in the LICENSE.txt file included with this file.
-
+"use strict";
 
 const Player = Module("player", {
     init: function init() {
diff --git a/pentadactyl/content/config.js b/pentadactyl/content/config.js
index 81a314d9..507741d8 100644
--- a/pentadactyl/content/config.js
+++ b/pentadactyl/content/config.js
@@ -4,6 +4,7 @@
 //
 // This work is licensed for reuse under an MIT license. Details are
 // given in the LICENSE.txt file included with this file.
+"use strict";
 
 const Config = Module("config", ConfigBase, {
     get visualbellWindow() getBrowser().mPanelContainer,
diff --git a/teledactyl/content/addressbook.js b/teledactyl/content/addressbook.js
index 00401853..48bbdaa2 100644
--- a/teledactyl/content/addressbook.js
+++ b/teledactyl/content/addressbook.js
@@ -2,6 +2,7 @@
 //
 // This work is licensed for reuse under an MIT license. Details are
 // given in the LICENSE.txt file included with this file.
+"use strict";
 
 const Addressbook = Module("addressbook", {
     init: function () {
diff --git a/teledactyl/content/compose/compose.js b/teledactyl/content/compose/compose.js
index ff73971f..90293701 100644
--- a/teledactyl/content/compose/compose.js
+++ b/teledactyl/content/compose/compose.js
@@ -2,6 +2,7 @@
 //
 // This work is licensed for reuse under an MIT license. Details are
 // given in the LICENSE.txt file included with this file.
+"use strict";
 
 function Compose() { //{{{
     ////////////////////////////////////////////////////////////////////////////////
diff --git a/teledactyl/content/config.js b/teledactyl/content/config.js
index d2183827..e47b5815 100644
--- a/teledactyl/content/config.js
+++ b/teledactyl/content/config.js
@@ -2,6 +2,7 @@
 //
 // This work is licensed for reuse under an MIT license. Details are
 // given in the LICENSE.txt file included with this file.
+"use strict";
 
 const Config = Module("config", ConfigBase, {
     init: function init() {
diff --git a/teledactyl/content/mail.js b/teledactyl/content/mail.js
index b13799d8..518c9bd6 100644
--- a/teledactyl/content/mail.js
+++ b/teledactyl/content/mail.js
@@ -2,6 +2,7 @@
 //
 // This work is licensed for reuse under an MIT license. Details are
 // given in the LICENSE.txt file included with this file.
+"use strict";
 
 const Mail = Module("mail", {
     init: function () {