diff --git a/src/APIHandler.py b/src/APIHandler.py
index 414772d..2526873 100644
--- a/src/APIHandler.py
+++ b/src/APIHandler.py
@@ -30,7 +30,7 @@ class APIHandler:
         elif response.status_code // 100 == 4:
             match response.status_code:
                 case 401|403:
-                    raise ConnectionError(f"Invalid API key or authentication method.")
+                    raise ConnectionError(f"Invalid API key, authentication method or elabid. Check if an item with ID = {elabid} actually exists.")
                 case 404:
                     raise ConnectionError(f"404: Not Found. This means there's no resource with this elabid (wrong elabid?) on your eLabFTW (wrong endpoint?).")
                 case 400: