diff --git a/src/Framework/Framework/Storage/FileSystemReturnedFileStorage.cs b/src/Framework/Framework/Storage/FileSystemReturnedFileStorage.cs
index d482296468..3ba836585c 100644
--- a/src/Framework/Framework/Storage/FileSystemReturnedFileStorage.cs
+++ b/src/Framework/Framework/Storage/FileSystemReturnedFileStorage.cs
@@ -97,12 +97,12 @@ private async Task StoreMetadata(Guid id, ReturnedFileMetadata metadata)
 
         private string GetDataFilePath(Guid id)
         {
-            return Path.Combine(TempDirectory, id + ".data");
+            return Path.Combine(TempDirectory, $"dotvvm-returned-file-{id}.data");
         }
 
         private string GetMetadataFilePath(Guid id)
         {
-            return Path.Combine(TempDirectory, id + ".metadata");
+            return Path.Combine(TempDirectory, $"dotvvm-returned-file-{id}.metadata");
         }
 
         public Task<ReturnedFile> GetFileAsync(Guid id)
@@ -142,7 +142,10 @@ public Task DeleteFileAsync(Guid id)
 
         public void DeleteOldFiles(DateTime maxCreatedDate)
         {
-            var files = Directory.GetFiles(TempDirectory).Where(t => File.GetCreationTime(t) < maxCreatedDate);
+            var files = Directory.GetFiles(TempDirectory)
+                .Where(t => File.GetCreationTime(t) < maxCreatedDate)
+                .Where(t => Path.GetFileName(t).StartsWith("dotvvm-returned-file-", StringComparison.OrdinalIgnoreCase));
+                
             foreach (var file in files)
             {
                 try
diff --git a/src/Framework/Framework/Storage/FileSystemUploadedFileStorage.cs b/src/Framework/Framework/Storage/FileSystemUploadedFileStorage.cs
index f8112a55bd..d85393e2df 100644
--- a/src/Framework/Framework/Storage/FileSystemUploadedFileStorage.cs
+++ b/src/Framework/Framework/Storage/FileSystemUploadedFileStorage.cs
@@ -24,6 +24,11 @@ public class FileSystemUploadedFileStorage : IUploadedFileStorage, IDisposable
         /// </summary>
         public FileSystemUploadedFileStorage(string tempDirectory, TimeSpan autoDeleteInterval)
         {
+            if (string.IsNullOrEmpty(tempDirectory))
+            {
+                throw new ArgumentNullException(nameof(tempDirectory));
+            }
+            
             TempDirectory = tempDirectory;
             AutoDeleteInterval = autoDeleteInterval;
 
@@ -95,6 +100,7 @@ public void DeleteOldFiles(DateTime maxCreatedDate)
             {
                 files = Directory.GetFiles(TempDirectory)
                     .Where(t => File.GetCreationTime(t) < maxCreatedDate)
+                    .Where(t => Path.GetFileName(t).StartsWith("dotvvm-uploaded-file-", StringComparison.OrdinalIgnoreCase))
                     .ToList();
             }
             catch (IOException)
@@ -121,7 +127,7 @@ public void DeleteOldFiles(DateTime maxCreatedDate)
         /// </summary>
         private string GetFileName(Guid id)
         {
-            return Path.Combine(TempDirectory, id + ".tmp");
+            return Path.Combine(TempDirectory, $"dotvvm-uploaded-file-{id}.tmp");
         }