diff --git a/manifests/init.pp b/manifests/init.pp
index 6a08359..ea84928 100644
--- a/manifests/init.pp
+++ b/manifests/init.pp
@@ -159,7 +159,9 @@
 #   Defaults to $::os_service_default
 #
 # [*control_exchange*]
-#   (Optional)
+#   (Optional) The default exchange under which topics are scoped. May be
+#   overridden by an exchange name specified in the transport_url
+#   option.
 #   Defaults to $::os_service_default
 #
 # [*rpc_response_timeout*]