diff --git a/Dockerfile b/Dockerfile
index 1308fcc..98dcb1a 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -12,4 +12,6 @@ FROM scratch
 COPY --from=builder /checker-delegation /checker-delegation
 USER 65534:65534
 EXPOSE 8080
+HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
+  CMD ["/checker-delegation", "-healthcheck"]
 ENTRYPOINT ["/checker-delegation"]
diff --git a/README.md b/README.md
index 6e1a5f4..db0667f 100644
--- a/README.md
+++ b/README.md
@@ -65,7 +65,7 @@ DNS queries to whatever name servers (and glue addresses) the parent
 zone advertises for the target. It is meant to run on a trusted network,
 reachable only by the happyDomain instance that drives it. Restrict
 access via a reverse proxy with authentication, a network ACL, or by
-binding the listener to a private interface — do not expose it directly
+binding the listener to a private interface; do not expose it directly
 to the public internet.
 
 ## Options
diff --git a/checker/dns.go b/checker/dns.go
index 0d23761..07f1325 100644
--- a/checker/dns.go
+++ b/checker/dns.go
@@ -248,4 +248,3 @@ func dsEqual(a, b *dns.DS) bool {
 		a.DigestType == b.DigestType &&
 		strings.EqualFold(a.Digest, b.Digest)
 }
-
diff --git a/checker/helpers_test.go b/checker/helpers_test.go
index f0bc26a..1773854 100644
--- a/checker/helpers_test.go
+++ b/checker/helpers_test.go
@@ -9,9 +9,9 @@ import (
 
 func TestDiffStringSets(t *testing.T) {
 	cases := []struct {
-		name              string
-		want, got         []string
-		missing, extra    []string
+		name           string
+		want, got      []string
+		missing, extra []string
 	}{
 		{
 			name:    "identical",
diff --git a/checker/rule.go b/checker/rule.go
index 26851cf..42f29c2 100644
--- a/checker/rule.go
+++ b/checker/rule.go
@@ -248,6 +248,13 @@ func (r *inBailiwickGlueRule) Evaluate(ctx context.Context, obs sdk.ObservationG
 	if errState != nil {
 		return errState
 	}
+	if len(data.ParentViews) == 0 {
+		return []sdk.CheckState{{
+			Status:  sdk.StatusUnknown,
+			Code:    "delegation_missing_glue",
+			Message: "no parent server was queried",
+		}}
+	}
 	var out []sdk.CheckState
 	for _, v := range data.ParentViews {
 		if v.UDPNSError != "" {
@@ -275,8 +282,13 @@ func (r *inBailiwickGlueRule) Evaluate(ctx context.Context, obs sdk.ObservationG
 			}
 		}
 	}
-	// No in-bailiwick NS means glue is not mandatory; stay silent rather
-	// than advertising a check that doesn't apply.
+	if len(out) == 0 {
+		return []sdk.CheckState{{
+			Status:  sdk.StatusOK,
+			Code:    "delegation_missing_glue",
+			Message: "no in-bailiwick NS, glue not required",
+		}}
+	}
 	return out
 }
 
diff --git a/checker/rule_test.go b/checker/rule_test.go
index 62a050c..86327dc 100644
--- a/checker/rule_test.go
+++ b/checker/rule_test.go
@@ -109,9 +109,9 @@ func TestNSMatchesDeclaredRule(t *testing.T) {
 		DelegatedFQDN: "www.example.com.",
 		DeclaredNS:    []string{"ns1.example.net.", "ns2.example.net."},
 		ParentViews: []ParentView{
-			{Server: "p1:53", NS: []string{"ns1.example.net.", "ns2.example.net."}},                 // match
-			{Server: "p2:53", NS: []string{"ns1.example.net.", "ns3.example.net."}},                 // mismatch
-			{Server: "p3:53", UDPNSError: "timeout"},                                                // skipped
+			{Server: "p1:53", NS: []string{"ns1.example.net.", "ns2.example.net."}}, // match
+			{Server: "p2:53", NS: []string{"ns1.example.net.", "ns3.example.net."}}, // mismatch
+			{Server: "p3:53", UDPNSError: "timeout"},                                // skipped
 		},
 	}
 	states := evalRule(t, r, data, nil)
@@ -185,7 +185,7 @@ func TestUnnecessaryGlueRule(t *testing.T) {
 func TestDSPresentAtParentRule_RequireDS(t *testing.T) {
 	r := &dsPresentAtParentRule{}
 	data := &DelegationData{
-		DeclaredDS: []DSRecord{{KeyTag: 1, Algorithm: 8, DigestType: 2, Digest: "AAAA"}},
+		DeclaredDS:  []DSRecord{{KeyTag: 1, Algorithm: 8, DigestType: 2, Digest: "AAAA"}},
 		ParentViews: []ParentView{{Server: "p:53"}}, // no DS at parent
 	}
 	t.Run("default is informational", func(t *testing.T) {
@@ -382,8 +382,8 @@ func TestDNSKEYMatchesDSRule_Match(t *testing.T) {
 
 func TestDNSKEYMatchesDSRule_NoMatch(t *testing.T) {
 	key := &dns.DNSKEY{
-		Hdr:       dns.RR_Header{Name: "example.com.", Rrtype: dns.TypeDNSKEY, Class: dns.ClassINET},
-		Flags:     257, Protocol: 3, Algorithm: dns.RSASHA256,
+		Hdr:   dns.RR_Header{Name: "example.com.", Rrtype: dns.TypeDNSKEY, Class: dns.ClassINET},
+		Flags: 257, Protocol: 3, Algorithm: dns.RSASHA256,
 		PublicKey: "AwEAAcMnWBKLuvG/LwnPVykcmpvnntwxfshHlHRhlY0F3oz8AMcuF8gw" +
 			"2Ge56vG9oqVxTzHl4Ss2dEqCQOjFlOVo+pa3JwIO1lUzbQ==",
 	}
diff --git a/go.mod b/go.mod
index a589c05..02860ac 100644
--- a/go.mod
+++ b/go.mod
@@ -3,7 +3,7 @@ module git.happydns.org/checker-delegation
 go 1.25.0
 
 require (
-	git.happydns.org/checker-sdk-go v1.4.0
+	git.happydns.org/checker-sdk-go v1.5.0
 	github.com/miekg/dns v1.1.72
 )
 
diff --git a/go.sum b/go.sum
index fc3939b..2a80023 100644
--- a/go.sum
+++ b/go.sum
@@ -1,5 +1,5 @@
-git.happydns.org/checker-sdk-go v1.4.0 h1:sO8EnF3suhNgYLRsbmCZWJOymH/oNMrOUqj3FEzJArs=
-git.happydns.org/checker-sdk-go v1.4.0/go.mod h1:aNAcfYFfbhvH9kJhE0Njp5GX0dQbxdRB0rJ0KvSC5nI=
+git.happydns.org/checker-sdk-go v1.5.0 h1:5uD5Cm6xJ+lwnhbJ09iCXGHbYS9zRh+Yh0NeBHkAPBY=
+git.happydns.org/checker-sdk-go v1.5.0/go.mod h1:aNAcfYFfbhvH9kJhE0Njp5GX0dQbxdRB0rJ0KvSC5nI=
 github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
 github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/miekg/dns v1.1.72 h1:vhmr+TF2A3tuoGNkLDFK9zi36F2LS+hKTRW0Uf8kbzI=