diff --git a/sequencerclient/sequencerclient.go b/sequencerclient/sequencerclient.go
index 9ce8867..9adce89 100644
--- a/sequencerclient/sequencerclient.go
+++ b/sequencerclient/sequencerclient.go
@@ -68,6 +68,9 @@ func (c *Client) TryContribute(ctx context.Context, sessionID string) (*contribu
 	}
 	defer res.Body.Close()
 
+	if res.StatusCode == http.StatusUnauthorized {
+		return nil, false, fmt.Errorf("wrong or expired session-id, login again with the sequencer")
+	}
 	if res.StatusCode != http.StatusOK {
 		return nil, false, fmt.Errorf("received status code %d", res.StatusCode)
 	}