diff --git a/app/src/main/java/acr/browser/lightning/receiver/NetworkReceiver.java b/app/src/main/java/acr/browser/lightning/receiver/NetworkReceiver.java
index 2759353..97ffe38 100644
--- a/app/src/main/java/acr/browser/lightning/receiver/NetworkReceiver.java
+++ b/app/src/main/java/acr/browser/lightning/receiver/NetworkReceiver.java
@@ -5,13 +5,14 @@ import android.content.Context;
 import android.content.Intent;
 import android.net.ConnectivityManager;
 import android.net.NetworkInfo;
+import android.support.annotation.NonNull;
 
 public class NetworkReceiver extends BroadcastReceiver {
 
     @Override
     public void onReceive(Context context, Intent intent) {}
 
-    public static boolean isConnected(Context context) {
+    public static boolean isConnected(@NonNull Context context) {
         ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
         if (cm == null)
             return false;