diff --git a/dns/util.go b/dns/util.go
index 8259f22e..e53abab0 100644
--- a/dns/util.go
+++ b/dns/util.go
@@ -29,9 +29,11 @@ const (
 
 func putMsgToCache(c *cache.LruCache[string, *D.Msg], key string, msg *D.Msg) {
 	// skip dns cache for acme challenge
-	if q := msg.Question[0]; q.Qtype == D.TypeTXT && strings.HasPrefix(q.Name, "_acme-challenge") {
-		log.Debugln("[DNS] dns cache ignored because of acme challenge for: %s", q.Name)
-		return
+	if len(msg.Question) != 0 {
+		if q := msg.Question[0]; q.Qtype == D.TypeTXT && strings.HasPrefix(q.Name, "_acme-challenge") {
+			log.Debugln("[DNS] dns cache ignored because of acme challenge for: %s", q.Name)
+			return
+		}
 	}
 	var ttl uint32
 	switch {