diff --git a/mpcontribs-client/mpcontribs/client/__init__.py b/mpcontribs-client/mpcontribs/client/__init__.py
index be498771a..69ff4e8da 100644
--- a/mpcontribs-client/mpcontribs/client/__init__.py
+++ b/mpcontribs-client/mpcontribs/client/__init__.py
@@ -889,7 +889,7 @@ def __init__(
         if not apikey:
             apikey = os.environ.get("MPCONTRIBS_API_KEY", SETTINGS.get("PMG_MAPI_KEY"))
             if len(apikey) != 32:
-                raise MPContribsClientError("Invalid API key.")
+                raise MPContribsClientError(f"Invalid API key: {apikey}")
 
         if apikey and headers:
             apikey = None