diff --git a/services/core/java/com/android/server/connectivity/NetworkNotificationManager.java b/services/core/java/com/android/server/connectivity/NetworkNotificationManager.java
index 703e50a..0d935db 100644
--- a/services/core/java/com/android/server/connectivity/NetworkNotificationManager.java
+++ b/services/core/java/com/android/server/connectivity/NetworkNotificationManager.java
@@ -142,6 +142,18 @@
             extraInfo = null;
         }
 
+        // Clear any previous notification with lower priority, otherwise return. http://b/63676954.
+        // A new SIGN_IN notification with a new intent should override any existing one.
+        final int previousEventId = mNotificationTypeMap.get(id);
+        final NotificationType previousNotifyType = NotificationType.getFromId(previousEventId);
+        if (priority(previousNotifyType) > priority(notifyType)) {
+            Slog.d(TAG, String.format(
+                    "ignoring notification %s for network %s with existing notification %s",
+                    notifyType, id, previousNotifyType));
+            return;
+        }
+        clearNotification(id);
+
         if (DBG) {
             Slog.d(TAG, String.format(
                     "showNotification tag=%s event=%s transport=%s extraInfo=%s highPrioriy=%s",
@@ -274,4 +286,22 @@
         NotificationType t = NotificationType.getFromId(eventId);
         return (t != null) ? t.name() : "UNKNOWN";
     }
+
+    private static int priority(NotificationType t) {
+        if (t == null) {
+            return 0;
+        }
+        switch (t) {
+            case SIGN_IN:
+                return 4;
+            case NO_INTERNET:
+                return 3;
+            case NETWORK_SWITCH:
+                return 2;
+            case LOST_INTERNET:
+                return 1;
+            default:
+                return 0;
+        }
+    }
 }
diff --git a/tests/net/java/com/android/server/connectivity/NetworkNotificationManagerTest.java b/tests/net/java/com/android/server/connectivity/NetworkNotificationManagerTest.java
index f201bc7..911347c 100644
--- a/tests/net/java/com/android/server/connectivity/NetworkNotificationManagerTest.java
+++ b/tests/net/java/com/android/server/connectivity/NetworkNotificationManagerTest.java
@@ -16,6 +16,16 @@
 
 package com.android.server.connectivity;
 
+import static com.android.server.connectivity.NetworkNotificationManager.NotificationType.*;
+import static org.mockito.Mockito.any;
+import static org.mockito.Mockito.anyInt;
+import static org.mockito.Mockito.eq;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.reset;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
 import android.app.Notification;
 import android.app.NotificationManager;
 import android.content.Context;
@@ -37,15 +47,6 @@
 import org.mockito.Mockito;
 import org.mockito.MockitoAnnotations;
 
-import static com.android.server.connectivity.NetworkNotificationManager.NotificationType.*;
-import static org.mockito.Mockito.any;
-import static org.mockito.Mockito.anyInt;
-import static org.mockito.Mockito.eq;
-import static org.mockito.Mockito.never;
-import static org.mockito.Mockito.times;
-import static org.mockito.Mockito.verify;
-import static org.mockito.Mockito.when;
-
 public class NetworkNotificationManagerTest extends TestCase {
 
     static final NetworkCapabilities CELL_CAPABILITIES = new NetworkCapabilities();
@@ -140,4 +141,47 @@
 
         verify(mNotificationManager, never()).notifyAsUser(any(), anyInt(), any(), any());
     }
+
+    @SmallTest
+    public void testDuplicatedNotificationsNoInternetThenSignIn() {
+        final int id = 101;
+        final String tag = NetworkNotificationManager.tagFor(id);
+
+        // Show first NO_INTERNET
+        mManager.showNotification(id, NO_INTERNET, mWifiNai, mCellNai, null, false);
+        verify(mNotificationManager, times(1))
+                .notifyAsUser(eq(tag), eq(NO_INTERNET.eventId), any(), any());
+
+        // Captive portal detection triggers SIGN_IN a bit later, clearing the previous NO_INTERNET
+        mManager.showNotification(id, SIGN_IN, mWifiNai, mCellNai, null, false);
+        verify(mNotificationManager, times(1))
+                .cancelAsUser(eq(tag), eq(NO_INTERNET.eventId), any());
+        verify(mNotificationManager, times(1))
+                .notifyAsUser(eq(tag), eq(SIGN_IN.eventId), any(), any());
+
+        // Network disconnects
+        mManager.clearNotification(id);
+        verify(mNotificationManager, times(1)).cancelAsUser(eq(tag), eq(SIGN_IN.eventId), any());
+    }
+
+    @SmallTest
+    public void testDuplicatedNotificationsSignInThenNoInternet() {
+        final int id = 101;
+        final String tag = NetworkNotificationManager.tagFor(id);
+
+        // Show first SIGN_IN
+        mManager.showNotification(id, SIGN_IN, mWifiNai, mCellNai, null, false);
+        verify(mNotificationManager, times(1))
+                .notifyAsUser(eq(tag), eq(SIGN_IN.eventId), any(), any());
+        reset(mNotificationManager);
+
+        // NO_INTERNET arrives after, but is ignored.
+        mManager.showNotification(id, NO_INTERNET, mWifiNai, mCellNai, null, false);
+        verify(mNotificationManager, never()).cancelAsUser(any(), anyInt(), any());
+        verify(mNotificationManager, never()).notifyAsUser(any(), anyInt(), any(), any());
+
+        // Network disconnects
+        mManager.clearNotification(id);
+        verify(mNotificationManager, times(1)).cancelAsUser(eq(tag), eq(SIGN_IN.eventId), any());
+    }
 }