diff --git a/services/java/com/android/server/ConnectivityService.java b/services/java/com/android/server/ConnectivityService.java
index 4c22ae8..8c5ff04 100644
--- a/services/java/com/android/server/ConnectivityService.java
+++ b/services/java/com/android/server/ConnectivityService.java
@@ -412,8 +412,6 @@
                 ConnectivityManager.MAX_NETWORK_TYPE+1];
         mCurrentLinkProperties = new LinkProperties[ConnectivityManager.MAX_NETWORK_TYPE+1];
 
-        mNetworkPreference = getPersistedNetworkPreference();
-
         mRadioAttributes = new RadioAttributes[ConnectivityManager.MAX_RADIO_TYPE+1];
         mNetConfigs = new NetworkConfig[ConnectivityManager.MAX_NETWORK_TYPE+1];
 
@@ -495,6 +493,21 @@
             }
         }
 
+        // Update mNetworkPreference according to user mannually first then overlay config.xml
+        mNetworkPreference = getPersistedNetworkPreference();
+        if (mNetworkPreference == -1) {
+            for (int n : mPriorityList) {
+                if (mNetConfigs[n].isDefault() && ConnectivityManager.isNetworkTypeValid(n)) {
+                    mNetworkPreference = n;
+                    break;
+                }
+            }
+            if (mNetworkPreference == -1) {
+                throw new IllegalStateException(
+                        "You should set at least one default Network in config.xml!");
+            }
+        }
+
         mNetRequestersPids = new ArrayList[ConnectivityManager.MAX_NETWORK_TYPE+1];
         for (int i : mPriorityList) {
             mNetRequestersPids[i] = new ArrayList();
@@ -726,11 +739,8 @@
 
         final int networkPrefSetting = Settings.Global
                 .getInt(cr, Settings.Global.NETWORK_PREFERENCE, -1);
-        if (networkPrefSetting != -1) {
-            return networkPrefSetting;
-        }
 
-        return ConnectivityManager.DEFAULT_NETWORK_PREFERENCE;
+        return networkPrefSetting;
     }
 
     /**