diff --git a/src/StarfaceOutlookSync/Services/StarfaceApiClient.cs b/src/StarfaceOutlookSync/Services/StarfaceApiClient.cs
index 52997303..21234fa5 100644
--- a/src/StarfaceOutlookSync/Services/StarfaceApiClient.cs
+++ b/src/StarfaceOutlookSync/Services/StarfaceApiClient.cs
@@ -304,12 +304,27 @@ namespace StarfaceOutlookSync.Services
         {
             var sfContact = MapToStarface(contact);
             sfContact["id"] = contactId;
+
+            // Tag beibehalten
+            if (!string.IsNullOrEmpty(book.TagId))
+            {
+                sfContact["tags"] = new JArray { new JObject { ["id"] = book.TagId } };
+            }
+
             var query = "";
             if (book.Type == "user" && !string.IsNullOrEmpty(book.UserId))
                 query = $"?userId={book.UserId}";
 
-            var content = new StringContent(sfContact.ToString(), Encoding.UTF8, "application/json");
+            var body = sfContact.ToString();
+            var content = new StringContent(body, Encoding.UTF8, "application/json");
             var resp = await _http.PutAsync($"{_baseUrl}/contacts/{contactId}{query}", content);
+
+            if (!resp.IsSuccessStatusCode)
+            {
+                var respBody = await resp.Content.ReadAsStringAsync();
+                OnDebug?.Invoke($"PUT /contacts/{contactId} fehlgeschlagen: {(int)resp.StatusCode}\n{respBody}");
+            }
+
             return resp.IsSuccessStatusCode;
         }