diff --git a/apps/system/js/keyboard_manager.js b/apps/system/js/keyboard_manager.js
index e4a95f3368d4..35b84285eaa1 100644
--- a/apps/system/js/keyboard_manager.js
+++ b/apps/system/js/keyboard_manager.js
@@ -138,6 +138,7 @@ var KeyboardManager = {
     window.addEventListener('mozbrowsererror', this);
     window.addEventListener('applicationsetupdialogshow', this);
     window.addEventListener('mozmemorypressure', this);
+    window.addEventListener('lock', this);
 
     // To handle keyboard layout switching
     window.addEventListener('mozChromeEvent', function(evt) {
@@ -457,6 +458,14 @@ var KeyboardManager = {
           this._debug('mozmemorypressure event; keyboard removed');
         }
         break;
+
+      case 'lock':
+        if (this.hasActiveKeyboard) {
+          // Instead of hideKeyboard(), we should removeFocus() here.
+          // (and, removing the focus cause Gecko to ask us to hideKeyboard())
+          navigator.mozInputMethod.removeFocus();
+        }
+        break;
     }
   },
 
diff --git a/apps/system/test/unit/keyboard_manager_test.js b/apps/system/test/unit/keyboard_manager_test.js
index cfdfc3b09fc0..5609d33f6176 100644
--- a/apps/system/test/unit/keyboard_manager_test.js
+++ b/apps/system/test/unit/keyboard_manager_test.js
@@ -86,14 +86,21 @@ suite('KeyboardManager', function() {
   mocksHelperForKeyboardManager.attachTestHelpers();
 
   var realMozSettings = null;
+  var realKeyboard = null;
 
   suiteSetup(function() {
     document.body.innerHTML += '<div id="run-container"></div>';
     navigator.mozSettings = MockNavigatorSettings;
+
+    realKeyboard = window.navigator.mozInputMethod;
+    window.navigator.mozInputMethod = {
+      removeFocus: function() {}
+    };
   });
 
   suiteTeardown(function() {
     navigator.mozSettings = realMozSettings;
+    window.navigator.mozInputMethod = realKeyboard;
   });
 
   setup(function() {
@@ -488,6 +495,22 @@ suite('KeyboardManager', function() {
       trigger('applicationsetupdialogshow');
       assert.ok(hideKeyboardImmediately.called);
     });
+
+    test('lock event: do nothing if no keyboard', function() {
+      var spy = this.sinon.spy(navigator.mozInputMethod, 'removeFocus');
+      trigger('lock');
+      assert.ok(spy.notCalled);
+    });
+
+    test('lock event: hide keyboard if needed', function() {
+      var realActive = KeyboardManager.hasActiveKeyboard;
+      KeyboardManager.hasActiveKeyboard = true;
+      var spy = this.sinon.spy(navigator.mozInputMethod, 'removeFocus');
+      trigger('lock');
+      sinon.assert.calledOnce(spy);
+
+      KeyboardManager.hasActiveKeyboard = realActive;
+    });
   });
 
   suite('Hide Keyboard', function() {