diff --git a/roles/custom/matrix-bridge-mautrix-slack/defaults/main.yml b/roles/custom/matrix-bridge-mautrix-slack/defaults/main.yml
index ae03943a..4d8e3f2f 100644
--- a/roles/custom/matrix-bridge-mautrix-slack/defaults/main.yml
+++ b/roles/custom/matrix-bridge-mautrix-slack/defaults/main.yml
@@ -124,7 +124,7 @@ matrix_mautrix_slack_registration_yaml: |
   rate_limited: false
   namespaces:
       users:
-      - regex: '^@slack_[0-9]+:{{ matrix_mautrix_slack_homeserver_domain | regex_escape }}$'
+      - regex: '^@slack_[a-z-A-Z0-9\-]+:{{ matrix_mautrix_slack_homeserver_domain | regex_escape }}$'
         exclusive: true
       - exclusive: true
         regex: '^@{{ matrix_mautrix_slack_appservice_bot_username | regex_escape }}:{{ matrix_mautrix_slack_homeserver_domain | regex_escape }}$'