diff --git a/src/isomorphic/classic/class/ReactClass.js b/src/isomorphic/classic/class/ReactClass.js
index 7ba5f9ea21..160aa9d7dd 100644
--- a/src/isomorphic/classic/class/ReactClass.js
+++ b/src/isomorphic/classic/class/ReactClass.js
@@ -12,11 +12,8 @@
 'use strict';
 
 var ReactComponent = require('ReactComponent');
-var ReactCurrentOwner = require('ReactCurrentOwner');
 var ReactElement = require('ReactElement');
 var ReactErrorUtils = require('ReactErrorUtils');
-var ReactInstanceMap = require('ReactInstanceMap');
-var ReactLifeCycle = require('ReactLifeCycle');
 var ReactPropTypeLocations = require('ReactPropTypeLocations');
 var ReactPropTypeLocationNames = require('ReactPropTypeLocationNames');
 var ReactUpdateQueue = require('ReactUpdateQueue');
@@ -728,27 +725,7 @@ var ReactClassMixin = {
    * @final
    */
   isMounted: function() {
-    if (__DEV__) {
-      var owner = ReactCurrentOwner.current;
-      if (owner !== null) {
-        warning(
-          owner._warnedAboutRefsInRender,
-          '%s is accessing isMounted inside its render() function. ' +
-          'render() should be a pure function of props and state. It should ' +
-          'never access something that requires stale data from the previous ' +
-          'render, such as refs. Move this logic to componentDidMount and ' +
-          'componentDidUpdate instead.',
-          owner.getName() || 'A component'
-        );
-        owner._warnedAboutRefsInRender = true;
-      }
-    }
-    var internalInstance = ReactInstanceMap.get(this);
-    if (internalInstance) {
-      return internalInstance !== ReactLifeCycle.currentlyMountingInstance;
-    } else {
-      return false;
-    }
+    return ReactUpdateQueue.isMounted(this);
   },
 
   /**
diff --git a/src/renderers/shared/reconciler/ReactUpdateQueue.js b/src/renderers/shared/reconciler/ReactUpdateQueue.js
index d293bc9bc3..613cfaead1 100644
--- a/src/renderers/shared/reconciler/ReactUpdateQueue.js
+++ b/src/renderers/shared/reconciler/ReactUpdateQueue.js
@@ -72,6 +72,37 @@ function getInternalInstanceReadyForUpdate(publicInstance, callerName) {
  */
 var ReactUpdateQueue = {
 
+  /**
+   * Checks whether or not this composite component is mounted.
+   * @param {ReactClass} publicInstance The instance we want to test.
+   * @return {boolean} True if mounted, false otherwise.
+   * @protected
+   * @final
+   */
+  isMounted: function(publicInstance) {
+    if (__DEV__) {
+      var owner = ReactCurrentOwner.current;
+      if (owner !== null) {
+        warning(
+          owner._warnedAboutRefsInRender,
+          '%s is accessing isMounted inside its render() function. ' +
+          'render() should be a pure function of props and state. It should ' +
+          'never access something that requires stale data from the previous ' +
+          'render, such as refs. Move this logic to componentDidMount and ' +
+          'componentDidUpdate instead.',
+          owner.getName() || 'A component'
+        );
+        owner._warnedAboutRefsInRender = true;
+      }
+    }
+    var internalInstance = ReactInstanceMap.get(publicInstance);
+    if (internalInstance) {
+      return internalInstance !== ReactLifeCycle.currentlyMountingInstance;
+    } else {
+      return false;
+    }
+  },
+
   /**
    * Enqueue a callback that will be executed after all the pending updates
    * have processed.