log4net input should include global and logical thread context data

I have a simple eventflow setup writing to elasticsearch with log4net input

class Program
{
static void Main(string[] args)
{
using (var pipeline = DiagnosticPipelineFactory.CreatePipeline(".\\eventFlowConfig.json"))
{
var logger = LogManager.GetLogger("EventFlowRepo", "MY_LOGGER_NAME");
using (LogicalThreadContext.Stacks["NDC"].Push("12345"))
{
logger.Debug("Hey! Listen!", new Exception("uhoh"));
}
}
Console.ReadLine();
}
}
eventflowconfig.json

{
"inputs": [
{
"type": "Log4net",
"logLevel": "Debug"
},
{
"type": "Log4net",
"logLevel": "Info"
},
{
"type": "Log4net",
"logLevel": "Warn"
},
{
"type": "Log4net",
"logLevel": "Error"
},
{
"type": "Log4net",
"logLevel": "Fatal"
}
],
"outputs": [
{
"type": "ElasticSearch",
"indexNamePrefix": "defaultindex",
"serviceUri": "http://servername:9200",
"basicAuthenticationUserName": "user",
"basicAuthenticationUserPassword": "password",
"eventDocumentTypeName": "diagData",
"numberOfShards": 1,
"numberOfReplicas": 0,
"refreshInterval": "5s"
}
],
"settings": {
"pipelineBufferSize": "1000",
"maxEventBatchSize": "100",
"maxBatchDelayMsec": "500",
"maxConcurrency": "8",
"pipelineCompletionTimeoutMsec": "30000"
},
"extensions": []
}

The issue is, the custom data [12345 in this case] I write to the NDC context, is not written to elasticsearch. How do I configure elastic output to recognize any custom data pushed to NDC?
The debug message along with the "exception" message does get written to ELK