--- a/plugins/mod_websocket.lua	Tue May 16 17:51:33 2017 +0200
+++ b/plugins/mod_websocket.lua	Tue May 16 17:52:29 2017 +0200
@@ -334,7 +334,7 @@
 		-- This might be weird with random load order
 		local_cross_domain:exclude(cross_domain);
 		cross_domain:include(local_cross_domain);
-		module:log("debug", "cross_domain = %s", cross_domain);
+		module:log("debug", "cross_domain = %s", tostring(cross_domain));
 		function module.unload()
 			cross_domain:exclude(local_cross_domain);
 		end