diff --git a/messagix/mercury.go b/messagix/mercury.go
index fa3f74d..318af8e 100644
--- a/messagix/mercury.go
+++ b/messagix/mercury.go
@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"mime/multipart"
 	"net/textproto"
+	"strings"
 
 	"github.com/google/go-querystring/query"
 	"github.com/rs/zerolog"
@@ -53,6 +54,9 @@ func (c *Client) SendMercuryUploadRequest(ctx context.Context, threadID int64, m
 
 	_, respBody, err := c.MakeRequest(url, "POST", h, payload, types.NONE)
 	if err != nil {
+		if strings.Contains(err.Error(), "access token is no longer valid") {
+			return nil, ErrTokenInvalidated
+		}
 		return nil, fmt.Errorf("failed to send MercuryUploadRequest: %v", err)
 	}