diff --git a/mobile/src/main/java/com/github/shadowsocks/App.kt b/mobile/src/main/java/com/github/shadowsocks/App.kt
index 772938b9..197d75cc 100644
--- a/mobile/src/main/java/com/github/shadowsocks/App.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/App.kt
@@ -146,7 +146,7 @@ class App : Application() {
             val assetManager = assets
             for (dir in arrayOf("acl", "overture"))
                 try {
-                    for (file in assetManager.list(dir)) assetManager.open(dir + '/' + file).use { input ->
+                    for (file in assetManager.list(dir)) assetManager.open("$dir/$file").use { input ->
                         File(deviceContext.filesDir, file).outputStream().use { output -> input.copyTo(output) }
                     }
                 } catch (e: IOException) {
diff --git a/mobile/src/main/java/com/github/shadowsocks/bg/LocalDnsService.kt b/mobile/src/main/java/com/github/shadowsocks/bg/LocalDnsService.kt
index 9e42ea99..4c0d3cda 100644
--- a/mobile/src/main/java/com/github/shadowsocks/bg/LocalDnsService.kt
+++ b/mobile/src/main/java/com/github/shadowsocks/bg/LocalDnsService.kt
@@ -72,8 +72,7 @@ object LocalDnsService {
                         .put("MinimumTTL", 120)
                         .put("CacheSize", 4096)
                 val remoteDns = JSONArray(profile.remoteDns.split(",")
-                        .mapIndexed { i, dns -> makeDns("UserDef-" + i,
-                        dns.trim() + ":53", 9) })
+                        .mapIndexed { i, dns -> makeDns("UserDef-$i", dns.trim() + ":53", 9) })
                 val localDns = JSONArray(arrayOf(
                         makeDns("Primary-1", "208.67.222.222:443", 3, false),
                         makeDns("Primary-2", "119.29.29.29:53", 3, false),