diff --git a/swh/journal/client.py b/swh/journal/client.py
--- a/swh/journal/client.py
+++ b/swh/journal/client.py
@@ -62,14 +62,14 @@
             object_types = ACCEPTED_OBJECT_TYPES
         if auto_offset_reset not in ACCEPTED_OFFSET_RESET:
             raise ValueError(
-                'Option \'auto_offset_reset\' only accept %s.' %
-                ACCEPTED_OFFSET_RESET)
+                'Option \'auto_offset_reset\' only accept %s, not %s' %
+                (ACCEPTED_OFFSET_RESET, auto_offset_reset))
 
         for object_type in object_types:
             if object_type not in ACCEPTED_OBJECT_TYPES:
                 raise ValueError(
-                    'Option \'object_types\' only accepts %s.' %
-                    ACCEPTED_OFFSET_RESET)
+                    'Option \'object_types\' only accepts %s, not %s.' %
+                    (ACCEPTED_OBJECT_TYPES, object_type))
 
         self.value_deserializer = kafka_to_value