diff --git a/checker/collect.go b/checker/collect.go
index 05134da..c0a1887 100644
--- a/checker/collect.go
+++ b/checker/collect.go
@@ -32,7 +32,7 @@ func (p *authoritativeConsistencyProvider) Collect(ctx context.Context, opts sdk
 	data := &ObservationData{
 		Zone:       dns.Fqdn(zone),
 		HasSOA:     svc.SOA != nil,
-		DeclaredNS: normalizeNSList(svc.NameServers),
+		DeclaredNS: normalizeNSList(svc.NameServers, zone),
 		Results:    map[string]*NSResult{},
 	}
 	if svc.SOA != nil {
@@ -167,13 +167,17 @@ func loadZone(opts sdk.CheckerOptions, svc *originService) (string, error) {
 	return "", fmt.Errorf("no zone name provided (missing 'domain_name' option and SOA header)")
 }
 
-func normalizeNSList(ns []*dns.NS) []string {
+func normalizeNSList(ns []*dns.NS, origin string) []string {
 	out := make([]string, 0, len(ns))
 	for _, n := range ns {
 		if n == nil {
 			continue
 		}
-		out = append(out, strings.ToLower(dns.Fqdn(n.Ns)))
+		name := n.Ns
+		if !strings.HasSuffix(name, ".") {
+			name = sdk.JoinRelative(name, strings.TrimSuffix(origin, "."))
+		}
+		out = append(out, strings.ToLower(dns.Fqdn(name)))
 	}
 	sort.Strings(out)
 	return out
diff --git a/checker/collect_test.go b/checker/collect_test.go
index 94db089..e9b8bed 100644
--- a/checker/collect_test.go
+++ b/checker/collect_test.go
@@ -80,13 +80,15 @@ func TestDiffStringSets_Equal(t *testing.T) {
 }
 
 func TestNormalizeNSList(t *testing.T) {
+	// Relative labels (no trailing dot) are joined with the zone origin.
+	// Absolute FQDNs (trailing dot) are kept as-is.
 	in := []*dns.NS{
-		{Ns: "NS2.Example.COM"},
+		{Ns: "ns2"},
 		nil,
 		{Ns: "ns1.example.com."},
-		{Ns: "NS1.example.com"},
+		{Ns: "ns1"},
 	}
-	got := normalizeNSList(in)
+	got := normalizeNSList(in, "example.com.")
 	want := []string{"ns1.example.com.", "ns1.example.com.", "ns2.example.com."}
 	if !reflect.DeepEqual(got, want) {
 		t.Errorf("got %v, want %v", got, want)
diff --git a/checker/definition.go b/checker/definition.go
index 32798e9..29a339f 100644
--- a/checker/definition.go
+++ b/checker/definition.go
@@ -110,6 +110,11 @@ func (p *authoritativeConsistencyProvider) Definition() *sdk.CheckerDefinition {
 					Label:    "Origin service",
 					AutoFill: sdk.AutoFillService,
 				},
+				{
+					Id:       "domain_name",
+					Label:    "Zone name",
+					AutoFill: sdk.AutoFillDomainName,
+				},
 			},
 		},
 		Rules: Rules(),