diff --git a/handlers.go b/handlers.go
index aac7cc0..4331657 100644
--- a/handlers.go
+++ b/handlers.go
@@ -71,6 +71,10 @@ func handleCmdJoin(sv *Server, msg *irc.Message) {
 	first := false
 	clid := strings.ToLower(msg.Pre)
 	chid := strings.ToLower(msg.Args[0])
+	if !strings.HasPrefix(chid, "#") {
+		sv.sendReply(msg.Pre, ERR_NOSUCHCHANNEL, msg.Args[0], "No such channel")
+		return
+	}
 	if _, exists := sv.chUsers[chid]; !exists {
 		sv.chUsers[chid] = make(map[string]string)
 		sv.chTopics[chid] = ""