I'm facing the following error in Heat:

ERROR: Property error : server1: image 'NoneType' object has no attribute 'rstrip'

and

2014-08-01 16:02:26.031 9086 TRACE heat.engine.parser     raise exception.StackValidationFailed(message=msg)
2014-08-01 16:02:26.031 9086 TRACE heat.engine.parser StackValidationFailed: Property error : server1: image 'NoneType' object has no attribute 'rstrip'

using the following template

heat_template_version: 2013-05-23
description: Test Template
parameters:
  ImageID:
    type: string
    description: Image use to boot a server
  NetID:
    type: string
    description: Network ID for the server
resources:
  server1:
    type: OS::Nova::Server
    properties:
      name: "Testserver"
      image: { get_param: ImageID }
      flavor: "m1.tiny"
      networks:
      - network: { get_param: NetID }
outputs:
  server1_private_ip:
    description: IP address of the server in the private network
    value: { get_attr: [ server1, first_address ] }

I tried UUID, Name in image property. Nothing helps. Is there anyone who can take a quick look and tell me what is wrong with that template? heat validate-template says it's ok.