diff --git a/internal/dnsforward/dns.go b/internal/dnsforward/dns.go
index c6c5a6b6..4a47cdc1 100644
--- a/internal/dnsforward/dns.go
+++ b/internal/dnsforward/dns.go
@@ -41,6 +41,12 @@ func (s *Server) handleDNSRequest(_ *proxy.Proxy, d *proxy.DNSContext) error {
 	ctx.startTime = time.Now()
 
 	type modProcessFunc func(ctx *dnsContext) int
+
+	// Since (*dnsforward.Server).handleDNSRequest(...) is used as
+	// proxy.(Config).RequestHandler, there is no need for additional index
+	// out of range checking in any of the following functions, because the
+	// (*proxy.Proxy).handleDNSRequest method performs it before calling the
+	// appropriate handler.
 	mods := []modProcessFunc{
 		processInitial,
 		processInternalHosts,
diff --git a/internal/dnsforward/msg.go b/internal/dnsforward/msg.go
index 28a8ac3a..71497a6c 100644
--- a/internal/dnsforward/msg.go
+++ b/internal/dnsforward/msg.go
@@ -11,7 +11,8 @@ import (
 	"github.com/miekg/dns"
 )
 
-// Create a DNS response by DNS request and set necessary flags
+// makeResponse creates a DNS response by req and sets necessary flags.  It also
+// guarantees that req.Question will be not empty.
 func (s *Server) makeResponse(req *dns.Msg) (resp *dns.Msg) {
 	resp = &dns.Msg{
 		MsgHdr: dns.MsgHdr{