diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 5d281db..1862b68 100755
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -10,7 +10,7 @@ before_script:
 
 build:
   stage: build
-  image: mcr.microsoft.com/dotnet/sdk:8.0
+  image: mcr.microsoft.com/dotnet/sdk:9.0-bookworm-slim
   script:
     - dotnet nuget add source https://pkgs.dev.azure.com/tgbots/Telegram.Bot/_packaging/release/nuget/v3/index.json -n Telegram.Bot
     - dotnet restore --no-cache
diff --git a/Services/HandlePostAction.cs b/Services/HandlePostAction.cs
index ebd438a..8836b31 100755
--- a/Services/HandlePostAction.cs
+++ b/Services/HandlePostAction.cs
@@ -59,7 +59,7 @@ namespace mstdnCats.Services
                         , replyMarkup: new InlineKeyboardMarkup(InlineKeyboardButton.WithUrl("View on Mastodon", post.Url)));
 
                         await _bot.AnswerCallbackQuery(callbackQuery.Id, "Media attachment approved and sent to channel.");
-                        await _bot.DeleteMessage(callbackQuery.Message.Chat.Id, callbackQuery.Message.MessageId);
+                        await _bot.DeleteMessage(callbackQuery.Message.Chat.Id, callbackQuery.Message.Id);
 
                         logger?.LogTrace($"Media attachment {mediaId} approved.");
 
@@ -84,7 +84,7 @@ namespace mstdnCats.Services
                 if (post.MediaAttachments.Count == 1 && post.MediaAttachments.First().MediaId == mediaId)
                 {
                     await _bot.AnswerCallbackQuery(callbackQuery.Id, "Post has only one attachment. No deletion performed.");
-                    await _bot.DeleteMessage(callbackQuery.Message.Chat.Id, callbackQuery.Message.MessageId);
+                    await _bot.DeleteMessage(callbackQuery.Message.Chat.Id, callbackQuery.Message.Id);
 
                     logger?.LogTrace($"Post {post.mstdnPostId} has only one attachment. No deletion performed.");
                 }
@@ -93,7 +93,7 @@ namespace mstdnCats.Services
                     post.MediaAttachments.RemoveAll(m => m.MediaId == mediaId);
                     await _db.UpdateOneAsync(p => p.mstdnPostId == post.mstdnPostId, post);
                     await _bot.AnswerCallbackQuery(callbackQuery.Id, "Media attachment rejected.");
-                    await _bot.DeleteMessage(callbackQuery.Message.Chat.Id, callbackQuery.Message.MessageId);
+                    await _bot.DeleteMessage(callbackQuery.Message.Chat.Id, callbackQuery.Message.Id);
 
                     logger?.LogTrace($"Media attachment {mediaId} removed from post {post.mstdnPostId}.");
                 }
diff --git a/mstdnCats.csproj b/mstdnCats.csproj
index 2b7e990..b288de2 100755
--- a/mstdnCats.csproj
+++ b/mstdnCats.csproj
@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFramework>net9.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
     <JsonSerializerIsReflectionEnabledByDefault>true</JsonSerializerIsReflectionEnabledByDefault>