diff --git a/briar-android/src/main/java/org/briarproject/briar/android/settings/SettingsFragment.java b/briar-android/src/main/java/org/briarproject/briar/android/settings/SettingsFragment.java
index 51d75e74d..6f4e053be 100644
--- a/briar-android/src/main/java/org/briarproject/briar/android/settings/SettingsFragment.java
+++ b/briar-android/src/main/java/org/briarproject/briar/android/settings/SettingsFragment.java
@@ -44,6 +44,7 @@ import org.briarproject.briar.android.navdrawer.NavDrawerActivity;
 import org.briarproject.briar.android.util.UiUtils;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 import java.util.Locale;
 import java.util.logging.Logger;
@@ -210,6 +211,13 @@ public class SettingsFragment extends PreferenceFragmentCompat
 					return true;
 				});
 
+		if (SDK_INT < 27) {
+			// remove System Default Theme option
+			List<CharSequence> entries =
+					new ArrayList<>(Arrays.asList(theme.getEntries()));
+			entries.remove(getString(R.string.pref_theme_system));
+			theme.setEntries(entries.toArray(new CharSequence[0]));
+		}
 		if (IS_DEBUG_BUILD) {
 			findPreference("pref_key_explode").setOnPreferenceClickListener(
 					preference -> {
diff --git a/briar-android/src/main/res/values/arrays.xml b/briar-android/src/main/res/values/arrays.xml
index 0a1c103ed..4171ab66c 100644
--- a/briar-android/src/main/res/values/arrays.xml
+++ b/briar-android/src/main/res/values/arrays.xml
@@ -63,10 +63,10 @@
 		<item>@string/pref_theme_auto</item>
 		<item>@string/pref_theme_system</item>
 	</string-array>
-	<string name="pref_theme_light_value">light</string>
-	<string name="pref_theme_dark_value">dark</string>
-	<string name="pref_theme_auto_value">auto</string>
-	<string name="pref_theme_system_value">system</string>
+	<string name="pref_theme_light_value" translatable="false">light</string>
+	<string name="pref_theme_dark_value" translatable="false">dark</string>
+	<string name="pref_theme_auto_value" translatable="false">auto</string>
+	<string name="pref_theme_system_value" translatable="false">system</string>
 	<string-array name="pref_theme_values">
 		<item>@string/pref_theme_light_value</item>
 		<item>@string/pref_theme_dark_value</item>
@@ -82,8 +82,8 @@
 		<item>@string/pref_lock_timeout_30</item>
 		<item>@string/pref_lock_timeout_60</item>
 	</string-array>
-	<string name="pref_lock_timeout_value_default">5</string>
-	<string name="pref_lock_timeout_value_never">-1</string>
+	<string name="pref_lock_timeout_value_default" translatable="false">5</string>
+	<string name="pref_lock_timeout_value_never" translatable="false">-1</string>
 	<string-array name="pref_key_lock_timeout_values">
 		<item>@string/pref_lock_timeout_value_never</item>
 		<item>1</item>