diff --git a/matrix/buffer.py b/matrix/buffer.py
index ca62bfe..ce981b1 100644
--- a/matrix/buffer.py
+++ b/matrix/buffer.py
@@ -1073,6 +1073,7 @@ def add_user(self, user_id, date, is_state, force_add=False):
                 user.user_id.startswith("@whatsapp_") or
                 user.user_id.startswith("@facebook_") or
                 user.user_id.startswith("@telegram_") or
+                user.user_id.startswith("@signal_") or
                 user.user_id.startswith("@_telegram_") or
                 user.user_id.startswith("@_xmpp_") or
                 user.user_id.startswith("@irc_")):