diff --git a/packages/@aws-cdk/aws-ecs/lib/cluster.ts b/packages/@aws-cdk/aws-ecs/lib/cluster.ts
index b0154f3ec5d0b..95e0fd6eab340 100644
--- a/packages/@aws-cdk/aws-ecs/lib/cluster.ts
+++ b/packages/@aws-cdk/aws-ecs/lib/cluster.ts
@@ -87,9 +87,9 @@ export class Cluster extends cdk.Construct implements ICluster {
 
     const namespaceType = options.type !== undefined
       ? options.type
-      : cloudmap.NamespaceType.DnsPrivate;
+      : NamespaceType.PrivateDns;
 
-    const sdNamespace = namespaceType === cloudmap.NamespaceType.DnsPrivate ?
+    const sdNamespace = namespaceType === NamespaceType.PrivateDns ?
       new cloudmap.PrivateDnsNamespace(this, 'DefaultServiceDiscoveryNamespace', {
         name: options.name,
         vpc: this.vpc
@@ -446,7 +446,7 @@ export interface NamespaceOptions {
    *
    * @default PrivateDns
    */
-  readonly type?: cloudmap.NamespaceType.DnsPrivate | cloudmap.NamespaceType.DnsPublic;
+  readonly type?: NamespaceType
 
   /**
    * The Amazon VPC that you want to associate the namespace with. Required for Private DNS namespaces
@@ -455,3 +455,8 @@ export interface NamespaceOptions {
    */
   readonly vpc?: ec2.IVpcNetwork;
 }
+
+export enum NamespaceType {
+  PrivateDns = cloudmap.NamespaceType.DnsPrivate,
+  PublicDns = cloudmap.NamespaceType.DnsPublic
+}
diff --git a/packages/@aws-cdk/aws-ecs/test/ec2/test.ec2-service.ts b/packages/@aws-cdk/aws-ecs/test/ec2/test.ec2-service.ts
index 5103213256099..2195bdc80f017 100644
--- a/packages/@aws-cdk/aws-ecs/test/ec2/test.ec2-service.ts
+++ b/packages/@aws-cdk/aws-ecs/test/ec2/test.ec2-service.ts
@@ -5,7 +5,7 @@ import cloudmap = require('@aws-cdk/aws-servicediscovery');
 import cdk = require('@aws-cdk/cdk');
 import { Test } from 'nodeunit';
 import ecs = require('../../lib');
-import { BinPackResource, BuiltInAttributes, ContainerImage, NetworkMode } from '../../lib';
+import { BinPackResource, BuiltInAttributes, ContainerImage, NamespaceType, NetworkMode } from '../../lib';
 
 export = {
   "When creating an ECS Service": {
@@ -606,7 +606,7 @@ export = {
       // WHEN
       cluster.addDefaultCloudMapNamespace({
         name: 'foo.com',
-        type: cloudmap.NamespaceType.DnsPrivate
+        type: NamespaceType.PrivateDns
       });
 
       new ecs.Ec2Service(stack, 'Service', {
@@ -683,7 +683,7 @@ export = {
       // WHEN
       cluster.addDefaultCloudMapNamespace({
         name: 'foo.com',
-        type: cloudmap.NamespaceType.DnsPrivate
+        type: NamespaceType.PrivateDns
       });
 
       new ecs.Ec2Service(stack, 'Service', {
@@ -794,7 +794,7 @@ export = {
       // WHEN
       cluster.addDefaultCloudMapNamespace({
         name: 'foo.com',
-        type: cloudmap.NamespaceType.DnsPrivate
+        type: NamespaceType.PrivateDns
       });
 
       new ecs.Ec2Service(stack, 'Service', {
@@ -869,7 +869,7 @@ export = {
       // WHEN
       cluster.addDefaultCloudMapNamespace({
         name: 'foo.com',
-        type: cloudmap.NamespaceType.DnsPrivate
+        type: NamespaceType.PrivateDns
       });
 
       new ecs.Ec2Service(stack, 'Service', {
diff --git a/packages/@aws-cdk/aws-ecs/test/fargate/test.fargate-service.ts b/packages/@aws-cdk/aws-ecs/test/fargate/test.fargate-service.ts
index 005d79ea0a613..ec4bd3d47bb6d 100644
--- a/packages/@aws-cdk/aws-ecs/test/fargate/test.fargate-service.ts
+++ b/packages/@aws-cdk/aws-ecs/test/fargate/test.fargate-service.ts
@@ -5,7 +5,7 @@ import cloudmap = require('@aws-cdk/aws-servicediscovery');
 import cdk = require('@aws-cdk/cdk');
 import { Test } from 'nodeunit';
 import ecs = require('../../lib');
-import { ContainerImage } from '../../lib';
+import { ContainerImage, NamespaceType } from '../../lib';
 
 export = {
   "When creating a Fargate Service": {
@@ -281,7 +281,7 @@ export = {
       // WHEN
       cluster.addDefaultCloudMapNamespace({
         name: 'foo.com',
-        type: cloudmap.NamespaceType.DnsPrivate
+        type: NamespaceType.PrivateDns
       });
 
       new ecs.FargateService(stack, 'Service', {
@@ -341,7 +341,7 @@ export = {
       // WHEN
       cluster.addDefaultCloudMapNamespace({
         name: 'foo.com',
-        type: cloudmap.NamespaceType.DnsPrivate
+        type: NamespaceType.PrivateDns
       });
 
       new ecs.FargateService(stack, 'Service', {
diff --git a/packages/@aws-cdk/aws-ecs/test/test.ecs-cluster.ts b/packages/@aws-cdk/aws-ecs/test/test.ecs-cluster.ts
index 2ac92b9436a4f..ea4f4b0c218a5 100644
--- a/packages/@aws-cdk/aws-ecs/test/test.ecs-cluster.ts
+++ b/packages/@aws-cdk/aws-ecs/test/test.ecs-cluster.ts
@@ -244,4 +244,29 @@ export = {
 
     test.done();
   },
+
+  "throws if default service discovery namespace added more than once"(test: Test) {
+    // GIVEN
+    const stack = new cdk.Stack();
+    const vpc = new ec2.VpcNetwork(stack, 'MyVpc', {});
+
+    const cluster = new ecs.Cluster(stack, 'EcsCluster', { vpc });
+    cluster.addCapacity('DefaultAutoScalingGroup', {
+      instanceType: new ec2.InstanceType('t2.micro'),
+    });
+
+    // WHEN
+    cluster.addDefaultCloudMapNamespace({
+      name: "foo.com"
+    });
+
+    // THEN
+    test.throws(() => {
+      cluster.addDefaultCloudMapNamespace({
+        name: "foo.com"
+      });
+    }, /Can only add default namespace once./);
+
+    test.done();
+  },
 };