diff --git a/build.sbt b/build.sbt
index 0a17f489..e2d0e96a 100644
--- a/build.sbt
+++ b/build.sbt
@@ -4,7 +4,7 @@ import android.Dependencies.{apklib,aar}
 
 android.Plugin.androidBuild
 
-platformTarget in Android := "android-19"
+platformTarget in Android := "android-21"
 
 name := "shadowsocks"
 
diff --git a/src/main/AndroidManifest.xml b/src/main/AndroidManifest.xml
index e942af4c..470ced60 100644
--- a/src/main/AndroidManifest.xml
+++ b/src/main/AndroidManifest.xml
@@ -16,7 +16,7 @@
 
   <uses-sdk
       android:minSdkVersion="16"
-      android:targetSdkVersion="19"/>
+      android:targetSdkVersion="21"/>
 
   <application
       android:allowBackup="true"
diff --git a/src/main/scala/com/github/shadowsocks/Shadowsocks.scala b/src/main/scala/com/github/shadowsocks/Shadowsocks.scala
index d6151646..2071ce69 100644
--- a/src/main/scala/com/github/shadowsocks/Shadowsocks.scala
+++ b/src/main/scala/com/github/shadowsocks/Shadowsocks.scala
@@ -755,7 +755,6 @@ class Shadowsocks
   }
 
   private def setPreferenceEnabled(enabled: Boolean) {
-    val isRoot = status.getBoolean(Key.isRoot, false)
     for (name <- Shadowsocks.PROXY_PREFS) {
       val pref = findPreference(name)
       if (pref != null) {
@@ -767,7 +766,7 @@ class Shadowsocks
       if (pref != null) {
         if (Seq(Key.isGlobalProxy, Key.isTrafficStat, Key.proxyedApps)
           .contains(name)) {
-          pref.setEnabled(enabled && isRoot)
+          pref.setEnabled(enabled && !isVpnEnabled)
         } else {
           pref.setEnabled(enabled)
         }
@@ -875,8 +874,8 @@ class Shadowsocks
 
   def isVpnEnabled: Boolean = {
     if (vpnEnabled < 0) {
-      vpnEnabled = if (Build.VERSION.SDK_INT
-        >= Build.VERSION_CODES.ICE_CREAM_SANDWICH && !status.getBoolean(Key.isRoot, false)) {
+      vpnEnabled = if (Build.VERSION.SDK_INT == Build.VERSION_CODES.LOLLIPOP
+        || !status.getBoolean(Key.isRoot, false)) {
         1
       } else {
         0