diff --git a/back/src/Directory.Build.props b/back/src/Directory.Build.props
index a3c3d9d6..1d56c929 100644
--- a/back/src/Directory.Build.props
+++ b/back/src/Directory.Build.props
@@ -1,7 +1,7 @@
 <Project>
 	<PropertyGroup>
 		<TargetFramework>net7.0</TargetFramework>
-		<LangVersion>default</LangVersion>
+		<LangVersion>preview</LangVersion>
 		<Company>Kyoo</Company>
 		<Authors>Kyoo</Authors>
 		<Copyright>Copyright (c) Kyoo</Copyright>
diff --git a/back/src/Kyoo.Abstractions/Models/Exceptions/ItemNotFoundException.cs b/back/src/Kyoo.Abstractions/Models/Exceptions/ItemNotFoundException.cs
index f8a79486..0fd5825f 100644
--- a/back/src/Kyoo.Abstractions/Models/Exceptions/ItemNotFoundException.cs
+++ b/back/src/Kyoo.Abstractions/Models/Exceptions/ItemNotFoundException.cs
@@ -30,7 +30,8 @@ namespace Kyoo.Abstractions.Models.Exceptions
 		/// <summary>
 		/// Create a default <see cref="ItemNotFoundException"/> with no message.
 		/// </summary>
-		public ItemNotFoundException() { }
+		public ItemNotFoundException()
+			: base("Item not found") { }
 
 		/// <summary>
 		/// Create a new <see cref="ItemNotFoundException"/> with a message
diff --git a/back/src/Kyoo.Core/Controllers/ThumbnailsManager.cs b/back/src/Kyoo.Core/Controllers/ThumbnailsManager.cs
index fe0bda25..c1cbd727 100644
--- a/back/src/Kyoo.Core/Controllers/ThumbnailsManager.cs
+++ b/back/src/Kyoo.Core/Controllers/ThumbnailsManager.cs
@@ -219,17 +219,18 @@ namespace Kyoo.Core.Controllers
 			try
 			{
 				await using FileStream img = File.Open(
-					$"/metadata/user/${userId}.webp",
+					$"/metadata/user/{userId}.webp",
 					FileMode.Open
 				);
 				return img;
 			}
 			catch (FileNotFoundException) { }
+			catch (DirectoryNotFoundException) { }
 
 			User user = await users.Value.Get(userId);
 			if (user.Email == null) throw new ItemNotFoundException();
 			using MD5 md5 = MD5.Create();
-			string hash = Convert.ToHexString(md5.ComputeHash(Encoding.ASCII.GetBytes(user.Email)));
+			string hash = Convert.ToHexString(md5.ComputeHash(Encoding.ASCII.GetBytes(user.Email))).ToLower();
 			try
 			{
 				HttpClient client = clientFactory.CreateClient();
@@ -250,7 +251,8 @@ namespace Kyoo.Core.Controllers
 			info.ColorType = SKColorType.Rgba8888;
 			using SKBitmap original = SKBitmap.Decode(codec, info);
 			using SKBitmap ret = original.Resize(new SKSizeI(250, 250), SKFilterQuality.High);
-			await _WriteTo(ret, $"/metadata/user/${userId}.webp", 75);
+			Directory.CreateDirectory("/metadata/user");
+			await _WriteTo(ret, $"/metadata/user/{userId}.webp", 75);
 		}
 	}
 }
diff --git a/back/src/Kyoo.Core/ExceptionFilter.cs b/back/src/Kyoo.Core/ExceptionFilter.cs
index 98101283..cc625641 100644
--- a/back/src/Kyoo.Core/ExceptionFilter.cs
+++ b/back/src/Kyoo.Core/ExceptionFilter.cs
@@ -30,19 +30,12 @@ namespace Kyoo.Core
 	/// <summary>
 	/// A middleware to handle errors globally.
 	/// </summary>
-	public class ExceptionFilter : IExceptionFilter
+	/// <remarks>
+	/// Initializes a new instance of the <see cref="ExceptionFilter"/> class.
+	/// </remarks>
+	/// <param name="logger">The logger used to log errors.</param>
+	public class ExceptionFilter(ILogger<ExceptionFilter> logger) : IExceptionFilter
 	{
-		private readonly ILogger _logger;
-
-		/// <summary>
-		/// Initializes a new instance of the <see cref="ExceptionFilter"/> class.
-		/// </summary>
-		/// <param name="logger">The logger used to log errors.</param>
-		public ExceptionFilter(ILogger<ExceptionFilter> logger)
-		{
-			_logger = logger;
-		}
-
 		/// <inheritdoc/>
 		public void OnException(ExceptionContext context)
 		{
@@ -65,7 +58,7 @@ namespace Kyoo.Core
 					context.Result = new UnauthorizedObjectResult(new RequestError(ex.Message));
 					break;
 				case Exception ex:
-					_logger.LogError(ex, "Unhandled error");
+					logger.LogError(ex, "Unhandled error");
 					context.Result = new ServerErrorObjectResult(
 						new RequestError("Internal Server Error")
 					);