diff --git a/rootfs/etc/confd/templates/config.yaml.tmpl b/rootfs/etc/confd/templates/config.yaml.tmpl
index f08704d..b390fd3 100644
--- a/rootfs/etc/confd/templates/config.yaml.tmpl
+++ b/rootfs/etc/confd/templates/config.yaml.tmpl
@@ -32,7 +32,7 @@ appservice:
     tls_key: false
 
     # The hostname and port where this appservice should listen.
-    hostname: ::
+    hostname: [::]
     port: 29317
     # The maximum body size of appservice API requests (from the homeserver) in mebibytes
     # Usually 1 is enough, but on high-traffic bridges you might need to increase this to avoid 413s