diff --git a/buildman/manager/executor.py b/buildman/manager/executor.py
index e4f9fb7bb..54b689611 100644
--- a/buildman/manager/executor.py
+++ b/buildman/manager/executor.py
@@ -121,12 +121,14 @@ class EC2Executor(BuilderExecutor):
     block_devices = boto.ec2.blockdevicemapping.BlockDeviceMapping()
     block_devices['/dev/xvda'] = ssd_root_ebs
 
-    interface = boto.ec2.networkinterface.NetworkInterfaceSpecification(
-        subnet_id=self.executor_config['EC2_VPC_SUBNET_ID'],
-        groups=self.executor_config['EC2_SECURITY_GROUP_IDS'],
-        associate_public_ip_address=True,
-    )
-    interfaces = boto.ec2.networkinterface.NetworkInterfaceCollection(interface)
+    interfaces = None
+    if self.executor_config.get('EC2_VPC_SUBNET_ID', None) is not None:
+      interface = boto.ec2.networkinterface.NetworkInterfaceSpecification(
+          subnet_id=self.executor_config['EC2_VPC_SUBNET_ID'],
+          groups=self.executor_config['EC2_SECURITY_GROUP_IDS'],
+          associate_public_ip_address=True,
+      )
+      interfaces = boto.ec2.networkinterface.NetworkInterfaceCollection(interface)
 
     reservation = yield From(ec2_conn.run_instances(
         coreos_ami,