diff --git a/v2/account_claims.go b/v2/account_claims.go
index 5c1665d..fa8fc58 100644
--- a/v2/account_claims.go
+++ b/v2/account_claims.go
@@ -152,10 +152,20 @@ type Mapping map[Subject][]WeightedMapping
 func (m *Mapping) Validate(vr *ValidationResults) {
 	for ubFrom, wm := range (map[Subject][]WeightedMapping)(*m) {
 		ubFrom.Validate(vr)
+		perCluster := make(map[string]uint8)
 		total := uint8(0)
-		for _, wm := range wm {
-			wm.Subject.Validate(vr)
-			total += wm.GetWeight()
+		for _, e := range wm {
+			e.Subject.Validate(vr)
+			if e.Cluster != "" {
+				t := perCluster[e.Cluster]
+				t += e.Weight
+				perCluster[e.Cluster] = t
+				if t > 100 {
+					vr.AddError("Mapping %q in cluster %q exceeds 100%% among all of it's weighted to mappings", ubFrom, e.Cluster)
+				}
+			} else {
+				total += e.GetWeight()
+			}
 		}
 		if total > 100 {
 			vr.AddError("Mapping %q exceeds 100%% among all of it's weighted to mappings", ubFrom)
diff --git a/v2/account_claims_test.go b/v2/account_claims_test.go
index 19dbf93..c3cfa5e 100644
--- a/v2/account_claims_test.go
+++ b/v2/account_claims_test.go
@@ -709,6 +709,40 @@ func TestAccountMapping(t *testing.T) { // don't block encoding!!!
 	}
 }
 
+func TestAccountClusterMany100MappingOK(t *testing.T) { // don't block encoding!!!
+	akp := createAccountNKey(t)
+	apk := publicKey(akp, t)
+
+	account := NewAccountClaims(apk)
+	vr := &ValidationResults{}
+
+	account.AddMapping("q",
+		WeightedMapping{Subject: "qq", Weight: 100, Cluster: "A"},
+		WeightedMapping{Subject: "qq", Weight: 100, Cluster: "B"},
+		WeightedMapping{Subject: "bb", Weight: 100, Cluster: "C"},
+		WeightedMapping{Subject: "qq", Weight: 100})
+	account.Validate(vr)
+	if !vr.IsEmpty() {
+		t.Fatal("Expected no errors")
+	}
+}
+
+func TestAccountClusterNoOver100Mapping(t *testing.T) { // don't block encoding!!!
+	akp := createAccountNKey(t)
+	apk := publicKey(akp, t)
+
+	account := NewAccountClaims(apk)
+	vr := &ValidationResults{}
+
+	account.AddMapping("q",
+		WeightedMapping{Subject: "qq", Weight: 100, Cluster: "A"},
+		WeightedMapping{Subject: "qq", Weight: 5, Cluster: "A"})
+	account.Validate(vr)
+	if !vr.IsBlocking(false) {
+		t.Fatal("Expected blocking error as sum of weights is > 100")
+	}
+}
+
 func TestAccountExternalAuthorization(t *testing.T) {
 	akp := createAccountNKey(t)
 	apk := publicKey(akp, t)