diff --git a/app/src/main/java/io/github/wulkanowy/ui/base/ThemeManager.kt b/app/src/main/java/io/github/wulkanowy/ui/base/ThemeManager.kt
index 5b347fe81..501348612 100644
--- a/app/src/main/java/io/github/wulkanowy/ui/base/ThemeManager.kt
+++ b/app/src/main/java/io/github/wulkanowy/ui/base/ThemeManager.kt
@@ -3,6 +3,7 @@ package io.github.wulkanowy.ui.base
 import android.content.pm.PackageManager.GET_ACTIVITIES
 import androidx.appcompat.app.AppCompatActivity
 import androidx.appcompat.app.AppCompatDelegate
+import androidx.appcompat.app.AppCompatDelegate.MODE_NIGHT_FOLLOW_SYSTEM
 import androidx.appcompat.app.AppCompatDelegate.MODE_NIGHT_NO
 import androidx.appcompat.app.AppCompatDelegate.MODE_NIGHT_YES
 import io.github.wulkanowy.R
@@ -22,8 +23,12 @@ class ThemeManager @Inject constructor(private val preferencesRepository: Prefer
 
     fun applyDefaultTheme() {
         AppCompatDelegate.setDefaultNightMode(
-            if (preferencesRepository.appTheme == "light") MODE_NIGHT_NO
-            else MODE_NIGHT_YES
+            when (val theme = preferencesRepository.appTheme) {
+                "light" -> MODE_NIGHT_NO
+                "dark", "black" -> MODE_NIGHT_YES
+                "system" -> MODE_NIGHT_FOLLOW_SYSTEM
+                else -> throw IllegalArgumentException("Wrong theme: $theme")
+            }
         )
     }
 
diff --git a/app/src/main/res/values-pl-v29/preferences_values.xml b/app/src/main/res/values-pl-v29/preferences_values.xml
new file mode 100644
index 000000000..57f208044
--- /dev/null
+++ b/app/src/main/res/values-pl-v29/preferences_values.xml
@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources xmlns:tools="http://schemas.android.com/tools">
+    <string-array name="app_theme_entries" tools:ignore="InconsistentArrays">
+        <item>Motyw systemu</item>
+        <item>Jasny</item>
+        <item>Ciemny</item>
+        <item>Czarny (AMOLED)</item>
+    </string-array>
+</resources>
diff --git a/app/src/main/res/values-pl/preferences_values.xml b/app/src/main/res/values-pl/preferences_values.xml
index 868ead4d9..e4c30eb05 100644
--- a/app/src/main/res/values-pl/preferences_values.xml
+++ b/app/src/main/res/values-pl/preferences_values.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<resources>
+<resources xmlns:tools="http://schemas.android.com/tools">
     <string-array name="services_interval_entries">
         <item>15 minut</item>
         <item>30 minut</item>
@@ -10,7 +10,7 @@
         <item>24 godziny</item>
     </string-array>
 
-    <string-array name="app_theme_entries">
+    <string-array name="app_theme_entries" tools:ignore="InconsistentArrays">
         <item>Jasny</item>
         <item>Ciemny</item>
         <item>Czarny (AMOLED)</item>
diff --git a/app/src/main/res/values-v29/preferences_defaults.xml b/app/src/main/res/values-v29/preferences_defaults.xml
new file mode 100644
index 000000000..bb573d664
--- /dev/null
+++ b/app/src/main/res/values-v29/preferences_defaults.xml
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources xmlns:tools="http://schemas.android.com/tools" tools:ignore="MissingTranslation">
+    <string name="pref_default_app_theme">system</string>
+</resources>
diff --git a/app/src/main/res/values-v29/preferences_values.xml b/app/src/main/res/values-v29/preferences_values.xml
new file mode 100644
index 000000000..f27c1c69c
--- /dev/null
+++ b/app/src/main/res/values-v29/preferences_values.xml
@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources xmlns:tools="http://schemas.android.com/tools">
+    <string-array name="app_theme_entries" tools:ignore="InconsistentArrays">
+        <item>System theme</item>
+        <item>Light</item>
+        <item>Dark</item>
+        <item>Black (AMOLED)</item>
+    </string-array>
+    <string-array name="app_theme_values" translatable="false" tools:ignore="InconsistentArrays">
+        <item>system</item>
+        <item>light</item>
+        <item>dark</item>
+        <item>black</item>
+    </string-array>
+</resources>
diff --git a/app/src/main/res/values/preferences_values.xml b/app/src/main/res/values/preferences_values.xml
index 97396baad..289f14f34 100644
--- a/app/src/main/res/values/preferences_values.xml
+++ b/app/src/main/res/values/preferences_values.xml
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<resources>
+<resources xmlns:tools="http://schemas.android.com/tools">
     <string-array name="startup_tab_entries" translatable="false">
         <item>@string/grade_title</item>
         <item>@string/attendance_title</item>
@@ -13,12 +13,12 @@
         <item>3</item>
     </string-array>
 
-    <string-array name="app_theme_entries">
+    <string-array name="app_theme_entries" tools:ignore="InconsistentArrays">
         <item>Light</item>
         <item>Dark</item>
         <item>Black (AMOLED)</item>
     </string-array>
-    <string-array name="app_theme_values" translatable="false">
+    <string-array name="app_theme_values" translatable="false" tools:ignore="InconsistentArrays">
         <item>light</item>
         <item>dark</item>
         <item>black</item>