diff --git a/dom/inputmethod/MozKeyboard.js b/dom/inputmethod/MozKeyboard.js
index 3e1a305bb4a2..4c62a43707af 100644
--- a/dom/inputmethod/MozKeyboard.js
+++ b/dom/inputmethod/MozKeyboard.js
@@ -378,10 +378,6 @@ MozInputMethod.prototype = {
   },
 
   get mgmt() {
-    if (!WindowMap.isActive(this._window)) {
-      return null;
-    }
-
     return this._mgmt;
   },
 
diff --git a/dom/inputmethod/mochitest/mochitest.ini b/dom/inputmethod/mochitest/mochitest.ini
index 8bf45e99dba7..693b72d89067 100644
--- a/dom/inputmethod/mochitest/mochitest.ini
+++ b/dom/inputmethod/mochitest/mochitest.ini
@@ -7,4 +7,5 @@ support-files =
 
 [test_basic.html]
 [test_bug944397.html]
+[test_bug949059.html]
 [test_sendkey_cancel.html]
diff --git a/dom/inputmethod/mochitest/test_bug949059.html b/dom/inputmethod/mochitest/test_bug949059.html
new file mode 100644
index 000000000000..e929fa7f558a
--- /dev/null
+++ b/dom/inputmethod/mochitest/test_bug949059.html
@@ -0,0 +1,40 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+https://bugzilla.mozilla.org/show_bug.cgi?id=949059
+-->
+<head>
+  <title>Test "mgmt" property of MozInputMethod.</title>
+  <script type="application/javascript;version=1.7" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="application/javascript;version=1.7" src="inputmethod_common.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=949059">Mozilla Bug 949059</a>
+<p id="display"></p>
+<pre id="test">
+<script class="testbody" type="application/javascript;version=1.7">
+
+inputmethod_setup(function() {
+  runTest();
+});
+
+function runTest() {
+  let im = navigator.mozInputMethod;
+
+  // Treat current page as an input method and activate it.
+  SpecialPowers.wrap(im).setActive(true);
+  ok(im.mgmt, 'The mgmt property should not be null.');
+
+  // Deactivate current page.
+  SpecialPowers.wrap(im).setActive(false);
+  ok(im.mgmt, 'The mgmt property should not be null.');
+
+  inputmethod_cleanup();
+}
+
+</script>
+</pre>
+</body>
+</html>
+
