diff --git a/src/ui_interface.rs b/src/ui_interface.rs
index 7aab2c9e8..d7edf4efb 100644
--- a/src/ui_interface.rs
+++ b/src/ui_interface.rs
@@ -1297,7 +1297,9 @@ pub async fn change_id_shared(id: String, old_id: String) -> String {
 
 pub async fn change_id_shared_(id: String, old_id: String) -> &'static str {
     if !hbb_common::is_valid_custom_id(&id) {
-        log::debug!("debugging invalid id: \"{id}\", base64: \"{}\"", crate::encode64(&id));
+        log::debug!("debugging invalid id: \"{id}\", len: {}, base64: \"{}\"", id.len(), crate::encode64(&id));
+        let bom = id.trim_start_matches('\u{FEFF}');
+        log::debug!("bom: {}", hbb_common::is_valid_custom_id(&bom));
         return INVALID_FORMAT;
     }