diff --git a/src/client/pages/preferences/theme.vue b/src/client/pages/preferences/theme.vue
index 2111cd7ae..488935a0c 100644
--- a/src/client/pages/preferences/theme.vue
+++ b/src/client/pages/preferences/theme.vue
@@ -63,6 +63,7 @@ import MkSwitch from '../../components/ui/switch.vue';
 import i18n from '../../i18n';
 import { Theme, builtinThemes, applyTheme } from '../../theme';
 import { selectFile } from '../../scripts/select-file';
+import { isDeviceDarkmode } from '../../scripts/is-device-darkmode';
 
 export default Vue.extend({
 	i18n,
@@ -132,6 +133,12 @@ export default Vue.extend({
 			}
 		},
 
+		syncDeviceDarkMode() {
+			if (this.$store.state.device.syncDeviceDarkMode) {
+				this.$store.commit('device/set', { key: 'darkMode', value: isDeviceDarkmode() });
+			}
+		},
+
 		wallpaper() {
 			if (this.wallpaper == null) {
 				localStorage.removeItem('wallpaper');