kea is not accepting custom spaces in option definitions in class

options in kea can be defined in kea standard space dhcp4 and dhcp6 or custom spaces e.g.:

"option-def": [
  {
    "array": false,
    "code": 242,
    "encapsulate": "",
    "name": "dls",
    "record-types": "",
    "space": "XYZ",
    "type": "string"
  }
],

But Kea accept custom spaces only on global level, returns error with this configuration:

client-classes": [
    {
        "option-def": [
            {
                "encapsulate": "339", 
                "code": 43, 
                "type": "empty", 
                "name": "vendor-encapsulated-options"
            }, 
            {
                "code": 2, 
                "name": "vlanid", 
                "space": "339", 
                "type": "uint32", 
                "record-types": "", 
                "array": false, 
                "encapsulate": ""
            }, 
            {
                "code": 3, 
                "name": "dls", 
                "space": "339", 
                "type": "string", 
                "record-types": "", 
                "array": false, 
                "encapsulate": ""
            }
        ], 
        "name": "VENDOR_CLASS_339", 
        "option-data": [
            {
                "name": "vendor-encapsulated-options"
            }, 
            {
                "always-send": true, 
                "data": "123", 
                "name": "vlanid", 
                "space": "339"
            }, 
            {
                "always-send": true, 
                "data": "sdlp://192.0.2.11:18443", 
                "name": "dls", 
                "space": "339"
            }
        ]
    }
], 

Error:

2021-01-28 07:16:28.281 INFO  [kea-dhcp4.dhcp4/27394.140192072867456] DHCP4_STARTING Kea DHCPv4 server version 1.9.4-git (development) starting
2021-01-28 07:16:28.282 WARN  [kea-dhcp4.dhcp4/27394.140192072867456] DHCP4_DEVELOPMENT_VERSION This software is a development branch of Kea. It is not recommended for production use.
2021-01-28 07:16:28.283 ERROR [kea-dhcp4.dhcp4/27394.140192072867456] DHCP4_CONFIG_LOAD_FAIL configuration error using file: /home/wlodek/installed/git/etc/kea/kea-dhcp4.conf, reason: Not allowed option definition for code '2' in space '339' at (/home/wlodek/installed/git/etc/kea/kea-dhcp4.conf:46:21)
2021-01-28 07:16:28.285 ERROR [kea-dhcp4.dhcp4/27394.140192072867456] DHCP4_INIT_FAIL failed to initialize Kea server: configuration error using file '/home/wlodek/installed/git/etc/kea/kea-dhcp4.conf': Not allowed option definition for code '2' in space '339' at (/home/wlodek/installed/git/etc/kea/kea-dhcp4.conf:46:21)

Making impossible to have multiple suboptions code 2 for different classes. full config attached kea-dhcp4.conf