diff --git a/internal/listener/lrfc2136/listener.go b/internal/listener/lrfc2136/listener.go
index 183660e..faaf61b 100644
--- a/internal/listener/lrfc2136/listener.go
+++ b/internal/listener/lrfc2136/listener.go
@@ -219,6 +219,7 @@ func (a *Listener) handleXFR(ctx context.Context, q dns.Question, out chan *dns.
 				Hdr: dns.RR_Header{
 					Name:   q.Name,
 					Rrtype: dns.TypeSOA,
+					Class:  dns.ClassINET,
 				},
 				Ns:      q.Name,
 				Mbox:    q.Name,
diff --git a/internal/upstream/upstream.go b/internal/upstream/upstream.go
index d92b2e4..cf24229 100644
--- a/internal/upstream/upstream.go
+++ b/internal/upstream/upstream.go
@@ -81,6 +81,7 @@ func (r *Rule) RR() (dns.RR, error) {
 	hdr := dns.RR_Header{
 		Name:   r.Name,
 		Rrtype: r.Type,
+		Class:  dns.ClassINET,
 	}
 
 	switch r.Type {