diff --git a/mobile/src/main/java/be/mygod/vpnhotspot/App.kt b/mobile/src/main/java/be/mygod/vpnhotspot/App.kt
index dfabee80..12d387e5 100644
--- a/mobile/src/main/java/be/mygod/vpnhotspot/App.kt
+++ b/mobile/src/main/java/be/mygod/vpnhotspot/App.kt
@@ -30,7 +30,6 @@ class App : Application() {
             deviceContext.moveSharedPreferencesFrom(this, PreferenceManager.getDefaultSharedPreferencesName(this))
         } else deviceContext = this
         // workaround for support lib PreferenceDataStore bug
-        operatingChannel = operatingChannel
         dns = dns
         ServiceNotification.updateNotificationChannels()
     }
@@ -45,12 +44,10 @@ class App : Application() {
     val pref: SharedPreferences by lazy { PreferenceManager.getDefaultSharedPreferences(deviceContext) }
     val connectivity by lazy { getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager }
 
-    var operatingChannel: Int
-        get() {
-            val result = pref.getString(KEY_OPERATING_CHANNEL, null)?.toIntOrNull() ?: 0
-            return if (result in 0..165) result else 0
-        }
-        set(value) = pref.edit().putString(KEY_OPERATING_CHANNEL, value.toString()).apply()
+    val operatingChannel: Int get() {
+        val result = pref.getString(KEY_OPERATING_CHANNEL, null)?.toIntOrNull() ?: 0
+        return if (result in 1..165) result else 0
+    }
     var dns: String
         get() = pref.getString(KEY_DNS, "8.8.8.8")
         set(value) = pref.edit().putString(KEY_DNS, value).apply()
diff --git a/mobile/src/main/res/values-zh-rCN/strings.xml b/mobile/src/main/res/values-zh-rCN/strings.xml
index 71b4b87c..01c236c4 100644
--- a/mobile/src/main/res/values-zh-rCN/strings.xml
+++ b/mobile/src/main/res/values-zh-rCN/strings.xml
@@ -52,7 +52,7 @@
 
     <string name="settings_service">服务</string>
     <string name="settings_service_repeater_oc">Wi\u2011Fi 运行频段 (不稳定)</string>
-    <string name="settings_service_repeater_oc_summary">"%s (0 = 自动, 1\u201114 = 2.4GHz, 15\u2011165 = 5GHz)"</string>
+    <string name="settings_service_repeater_oc_summary">"自动 (1\u201114 = 2.4GHz, 15\u2011165 = 5GHz)"</string>
     <string name="settings_service_repeater_strict">严格模式</string>
     <string name="settings_service_repeater_strict_summary">只允许通过 VPN 隧道的包通过</string>
     <string name="settings_service_dns">备用 DNS 服务器[:端口]</string>
diff --git a/mobile/src/main/res/values/strings.xml b/mobile/src/main/res/values/strings.xml
index 577fcbc5..319bbbf5 100644
--- a/mobile/src/main/res/values/strings.xml
+++ b/mobile/src/main/res/values/strings.xml
@@ -55,7 +55,7 @@
 
     <string name="settings_service">Service</string>
     <string name="settings_service_repeater_oc">Operating Wi\u2011Fi channel (unstable)</string>
-    <string name="settings_service_repeater_oc_summary">%s (0 = auto, 1\u201114 = 2.4GHz, 15\u2011165 = 5GHz)</string>
+    <string name="settings_service_repeater_oc_summary">Auto (1\u201114 = 2.4GHz, 15\u2011165 = 5GHz)</string>
     <string name="settings_service_repeater_strict">Strict mode</string>
     <string name="settings_service_repeater_strict_summary">Only allow packets that goes through VPN tunnel</string>
     <string name="settings_service_dns">Fallback DNS server[:port]</string>
diff --git a/mobile/src/main/res/xml/pref_settings.xml b/mobile/src/main/res/xml/pref_settings.xml
index 850be482..831b4596 100644
--- a/mobile/src/main/res/xml/pref_settings.xml
+++ b/mobile/src/main/res/xml/pref_settings.xml
@@ -1,15 +1,14 @@
 <?xml version="1.0" encoding="utf-8"?>
-<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android"
-                  xmlns:app="http://schemas.android.com/apk/res-auto">
+<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
     <PreferenceCategory
         android:title="@string/title_repeater">
         <AutoSummaryEditTextPreference
             android:key="service.repeater.oc"
             android:title="@string/settings_service_repeater_oc"
-            app:pref_summaryHasText="@string/settings_service_repeater_oc_summary"
+            android:summary="@string/settings_service_repeater_oc_summary"
+            android:hint="@string/settings_service_repeater_oc_summary"
             android:inputType="number"
-            android:maxLength="3"
-            android:defaultValue="0"/>
+            android:maxLength="3"/>
         <SwitchPreference
             android:key="service.repeater.strict"
             android:title="@string/settings_service_repeater_strict"