--- a/mod_http_muc_log/mod_http_muc_log.lua	Tue Nov 21 00:46:00 2017 +0100
+++ b/mod_http_muc_log/mod_http_muc_log.lua	Tue Nov 21 00:48:05 2017 +0100
@@ -245,7 +245,7 @@
 	elseif lazy then
 		next_when = datetime.date(day_start + 86400);
 		prev_when = datetime.date(day_start - 86400);
-	else
+	elseif first and last then
 
 		module:log("debug", "Find next date with messages");
 		next_when = find_once(room, { after = last }, 3);