diff --git a/ReactAndroid/src/androidTest/java/com/facebook/react/tests/core/ReactInstanceManagerTest.java b/ReactAndroid/src/androidTest/java/com/facebook/react/tests/core/ReactInstanceManagerTest.java
index e7cdff2453e92e..e03721be842f6c 100644
--- a/ReactAndroid/src/androidTest/java/com/facebook/react/tests/core/ReactInstanceManagerTest.java
+++ b/ReactAndroid/src/androidTest/java/com/facebook/react/tests/core/ReactInstanceManagerTest.java
@@ -6,6 +6,7 @@
 package com.facebook.react.tests.core;
 
 import android.app.Activity;
+import android.support.test.InstrumentationRegistry;
 import android.support.test.annotation.UiThreadTest;
 import android.support.test.rule.ActivityTestRule;
 import android.support.test.runner.AndroidJUnit4;
@@ -14,6 +15,7 @@
 import com.facebook.react.common.LifecycleState;
 import com.facebook.react.shell.MainReactPackage;
 import com.facebook.react.testing.ReactTestHelper;
+import org.junit.After;
 import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
@@ -43,6 +45,19 @@ public void setup() {
         .build();
   }
 
+  @After
+  public void tearDown() {
+    final ReactRootView reactRootView = mReactRootView;
+    final ReactInstanceManager reactInstanceManager = mReactInstanceManager;
+    InstrumentationRegistry.getInstrumentation().runOnMainSync(new Runnable() {
+      @Override
+      public void run() {
+        reactRootView.unmountReactApplication();
+        reactInstanceManager.destroy();
+      }
+    });
+  }
+
   @Test
   @UiThreadTest
   public void testMountUnmount() {
@@ -56,7 +71,6 @@ public void testMountUnmount() {
   public void testResume() throws InterruptedException {
     mReactInstanceManager.onHostResume(mActivityRule.getActivity());
     mReactRootView.startReactApplication(mReactInstanceManager, TEST_MODULE);
-    Thread.sleep(1000);
     mReactInstanceManager.onHostResume(mActivityRule.getActivity());
   }
 
@@ -65,7 +79,14 @@ public void testResume() throws InterruptedException {
   public void testRecreateContext() throws InterruptedException {
     mReactInstanceManager.onHostResume(mActivityRule.getActivity());
     mReactInstanceManager.createReactContextInBackground();
-    Thread.sleep(1000);
     mReactRootView.startReactApplication(mReactInstanceManager, TEST_MODULE);
   }
+
+  @Test
+  @UiThreadTest
+  public void testMountTwice() {
+    mReactInstanceManager.onHostResume(mActivityRule.getActivity());
+    mReactRootView.startReactApplication(mReactInstanceManager, TEST_MODULE);
+    mReactInstanceManager.attachRootView(mReactRootView);
+  }
 }
diff --git a/ReactAndroid/src/main/java/com/facebook/react/ReactInstanceManager.java b/ReactAndroid/src/main/java/com/facebook/react/ReactInstanceManager.java
index e79ef488c807d9..d791cfbe1e6b68 100644
--- a/ReactAndroid/src/main/java/com/facebook/react/ReactInstanceManager.java
+++ b/ReactAndroid/src/main/java/com/facebook/react/ReactInstanceManager.java
@@ -99,6 +99,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 import javax.annotation.Nullable;
 
 /**
@@ -134,8 +135,8 @@ public interface ReactInstanceEventListener {
     void onReactContextInitialized(ReactContext context);
   }
 
-  private final List<ReactRootView> mAttachedRootViews = Collections.synchronizedList(
-    new ArrayList<ReactRootView>());
+  private final Set<ReactRootView> mAttachedRootViews = Collections.synchronizedSet(
+    new HashSet<ReactRootView>());
 
   private volatile LifecycleState mLifecycleState;
 
@@ -1037,8 +1038,7 @@ public void run() {
         });
   }
 
-  private void attachRootViewToInstance(
-      final ReactRootView rootView) {
+  private void attachRootViewToInstance(final ReactRootView rootView) {
     Log.d(ReactConstants.TAG, "ReactInstanceManager.attachRootViewToInstance()");
     Systrace.beginSection(TRACE_TAG_REACT_JAVA_BRIDGE, "attachRootViewToInstance");
     UIManager uiManagerModule = UIManagerHelper.getUIManager(mCurrentReactContext, rootView.getUIManagerType());