diff --git a/labels.go b/labels.go
index aa43a303..ad190927 100644
--- a/labels.go
+++ b/labels.go
@@ -38,6 +38,9 @@ func SplitLabels(s string) []string {
 //
 // www.miek.nl. and miek.nl. have two labels in common: miek and nl
 // www.miek.nl. and www.bla.nl. have one label in common: nl
+// 
+// Domain s1 is a subdomain of s2 if
+// CompareLabels(s1, s2) == LenLabels(s1)
 func CompareLabels(s1, s2 string) (n int) {
 	l1 := SplitLabels(s1)
 	l2 := SplitLabels(s2)
@@ -58,3 +61,27 @@ func CompareLabels(s1, s2 string) (n int) {
 	}
 	return
 }
+
+// LenLabels returns the number of labels in a domain name
+func LenLabels(s string) (labels int) {
+	if s == "." {
+		return
+	}
+	last := byte('.')
+	lastlast := byte('.')
+	s = Fqdn(s) // Make fully qualified
+	for i := 0; i < len(s); i++ {
+		if s[i] == '.' {
+			if last == '\\' {
+				if lastlast != '\\' {
+					// do nothing
+					continue
+				}
+			}
+			labels++
+		}
+		lastlast = last
+		last = s[i]
+	}
+	return
+}
diff --git a/zone.go b/zone.go
index d5af3146..95923702 100644
--- a/zone.go
+++ b/zone.go
@@ -3,7 +3,7 @@ package dns
 // A structure for handling zone data
 
 import (
-	"github.com/sauerbraten/radix"
+	"radix"
 )
 
 // Zone represents a DNS zone. 
@@ -34,6 +34,8 @@ func NewZone(origin string) *Zone {
 }
 
 // Insert inserts an RR into the zone. Overwrites.
+// Out-of-zone data
+// Glue
 func (z *Zone) Insert(r RR) {
 	zd := z.Radix.Find(r.Header().Name)
 	if zd == nil {
@@ -46,19 +48,29 @@ func (z *Zone) Insert(r RR) {
 			zd.Signatures = append(zd.Signatures, r.(*RR_RRSIG))
 		default:
 			zd.RR[t] = append(zd.RR[t], r)
+			glueCheck(r)
 		}
 		z.Radix.Insert(r.Header().Name, zd)
 		return
 	}
 	switch t := r.Header().Rrtype; t {
 	case TypeRRSIG:
-		zd.(*ZoneData).Signatures = append(zd.(*ZoneData).Signatures, r.(*RR_RRSIG))
+		zd.Value.(*ZoneData).Signatures = append(zd.Value.(*ZoneData).Signatures, r.(*RR_RRSIG))
 	default:
-		zd.(*ZoneData).RR[t] = append(zd.(*ZoneData).RR[t], r)
+		zd.Value.(*ZoneData).RR[t] = append(zd.Value.(*ZoneData).RR[t], r)
 	}
 	return
 }
 
+func glueCheck(r RR) {
+	if n, ok := r.(*RR_NS); ok {
+		// Check if glue would be needed
+		if CompareLabels(r.Header().Name, n.Ns) == LenLabels(r.Header().Name) {
+			println("glue needed?", r.Header().Name, n.Ns)
+		}
+	}
+}
+
 func (z *Zone) Remove(r RR) {
 
 }