diff --git a/lib/entity/file.dart b/lib/entity/file.dart
index 49806b44..7206405b 100644
--- a/lib/entity/file.dart
+++ b/lib/entity/file.dart
@@ -508,6 +508,10 @@ class FileRepo {
   Future<List<File>> list(Account account, File root) =>
       dataSrc.list(account, root);
 
+  /// See [FileDataSource.listSingle]
+  Future<File> listSingle(Account account, File root) =>
+      dataSrc.listSingle(account, root);
+
   /// See [FileDataSource.remove]
   Future<void> remove(Account account, File file) =>
       dataSrc.remove(account, file);
@@ -575,6 +579,9 @@ abstract class FileDataSource {
   /// List all files under [f]
   Future<List<File>> list(Account account, File f);
 
+  /// List a single file [f]
+  Future<File> listSingle(Account account, File f);
+
   /// Remove file
   Future<void> remove(Account account, File f);
 
diff --git a/lib/entity/file/data_source.dart b/lib/entity/file/data_source.dart
index 95d14923..ae9240c2 100644
--- a/lib/entity/file/data_source.dart
+++ b/lib/entity/file/data_source.dart
@@ -16,7 +16,6 @@ import 'package:nc_photos/remote_storage_util.dart' as remote_storage_util;
 import 'package:nc_photos/string_extension.dart';
 import 'package:nc_photos/touch_token_manager.dart';
 import 'package:nc_photos/use_case/compat/v32.dart';
-import 'package:nc_photos/use_case/ls_single_file.dart';
 import 'package:path/path.dart' as path;
 import 'package:quiver/iterables.dart';
 import 'package:uuid/uuid.dart';
@@ -78,6 +77,12 @@ class FileWebdavDataSource implements FileDataSource {
     return files;
   }
 
+  @override
+  listSingle(Account account, File f) async {
+    _log.info("[listSingle] ${f.path}");
+    return (await list(account, f, depth: 0)).first;
+  }
+
   @override
   remove(Account account, File f) async {
     _log.info("[remove] ${f.path}");
@@ -250,6 +255,12 @@ class FileAppDbDataSource implements FileDataSource {
     });
   }
 
+  @override
+  listSingle(Account account, File f) {
+    _log.info("[listSingle] ${f.path}");
+    throw UnimplementedError();
+  }
+
   @override
   remove(Account account, File f) {
     _log.info("[remove] ${f.path}");
@@ -440,6 +451,11 @@ class FileCachedDataSource implements FileDataSource {
     }
   }
 
+  @override
+  listSingle(Account account, File f) {
+    return _remoteSrc.listSingle(account, f);
+  }
+
   @override
   remove(Account account, File f) async {
     await _appDbSrc.remove(account, f);
@@ -656,7 +672,7 @@ class _CacheManager {
         // compare the etag to see if the content has been updated
         var remoteEtag = f.etag;
         // if no etag supplied, we need to query it form remote
-        remoteEtag ??= (await LsSingleFile(remoteSrc)(account, f.path)).etag;
+        remoteEtag ??= (await remoteSrc.list(account, f, depth: 0)).first.etag;
         if (cacheEtag == remoteEtag) {
           _log.fine(
               "[_listCache] etag matched for ${AppDbFileEntry.toPath(account, f)}");
diff --git a/lib/use_case/ls_single_file.dart b/lib/use_case/ls_single_file.dart
index 40d1a4d9..457c7123 100644
--- a/lib/use_case/ls_single_file.dart
+++ b/lib/use_case/ls_single_file.dart
@@ -1,15 +1,11 @@
 import 'package:nc_photos/account.dart';
 import 'package:nc_photos/entity/file.dart';
-import 'package:nc_photos/entity/file/data_source.dart';
 
 class LsSingleFile {
-  LsSingleFile(this.dataSrc);
+  LsSingleFile(this.fileRepo);
 
-  Future<File> call(Account account, String path) async {
-    final files = await dataSrc.list(account, File(path: path), depth: 0);
-    assert(files.length == 1);
-    return files.first;
-  }
+  Future<File> call(Account account, String path) =>
+      fileRepo.listSingle(account, File(path: path));
 
-  final FileWebdavDataSource dataSrc;
+  final FileRepo fileRepo;
 }
diff --git a/lib/widget/root_picker.dart b/lib/widget/root_picker.dart
index db985f01..f36f04ca 100644
--- a/lib/widget/root_picker.dart
+++ b/lib/widget/root_picker.dart
@@ -5,6 +5,7 @@ import 'package:flutter/widgets.dart';
 import 'package:logging/logging.dart';
 import 'package:nc_photos/account.dart';
 import 'package:nc_photos/api/api_util.dart' as api_util;
+import 'package:nc_photos/app_db.dart';
 import 'package:nc_photos/app_localizations.dart';
 import 'package:nc_photos/entity/file.dart';
 import 'package:nc_photos/entity/file/data_source.dart';
@@ -57,12 +58,12 @@ class _RootPickerState extends State<RootPicker> {
 
   void _initAccount() async {
     try {
-      const fileSrc = FileWebdavDataSource();
+      final fileRepo = FileRepo(FileCachedDataSource(AppDb()));
       final files = <File>[];
       for (final r in widget.account.roots) {
         if (r.isNotEmpty) {
           _ensureInitDialog();
-          files.add(await LsSingleFile(fileSrc)(
+          files.add(await LsSingleFile(fileRepo)(
               widget.account, file_util.unstripPath(widget.account, r)));
         }
       }
diff --git a/test/mock_type.dart b/test/mock_type.dart
index 67a2c62b..2a3cfe4f 100644
--- a/test/mock_type.dart
+++ b/test/mock_type.dart
@@ -142,6 +142,11 @@ class MockFileRepo implements FileRepo {
     throw UnimplementedError();
   }
 
+  @override
+  Future<File> listSingle(Account account, File root) async {
+    throw UnimplementedError();
+  }
+
   @override
   Future<void> move(Account account, File f, String destination,
       {bool? shouldOverwrite}) {