diff --git a/backend/box/box.go b/backend/box/box.go
index 7a222b162..d47073703 100644
--- a/backend/box/box.go
+++ b/backend/box/box.go
@@ -323,7 +323,7 @@ func shouldRetry(ctx context.Context, resp *http.Response, err error) (bool, err
 	}
 	authRetry := false
 
-	if resp != nil && resp.StatusCode == 401 && len(resp.Header["Www-Authenticate"]) == 1 && strings.Index(resp.Header["Www-Authenticate"][0], "expired_token") >= 0 {
+	if resp != nil && resp.StatusCode == 401 && strings.Contains(resp.Header.Get("Www-Authenticate"), "expired_token") {
 		authRetry = true
 		fs.Debugf(nil, "Should retry: %v", err)
 	}