Sleuth baggage remote-fields error: No extra values are propagated

sleuth_sink_application.yml

spring:
  application:
    name: customer-service
  sleuth:
    baggage:
      remote-fields: principal
    log:
      slf4j:
        whitelisted-mdc-keys:
          - principal

sleuth_sink_span.java

public Customer create(@RequestBody @Valid CreateCustomerRequest request, @RequestHeader HttpHeaders headers) {
  // headers has x-b3-traceid , x-b3-spanid , x-b3-parentspanid and x-b3-sampled
  Span currentSpan = tracer.currentSpan();
  List<BaggageField> baggages = ExtraBaggageContext.getAllFields(currentSpan.context()); // empty
  Map<String, String> keys = BaggageField.getAllValues(currentSpan.context()); // empty
  CurrentTraceContext ctc = Tracing.current().currentTraceContext(); 
  String value = BaggageField.getByName(currentSpan.context(), "principal").getValue(); // NPE :)
  // ...
}

sleuth_source_application.yml

spring:
  application:
    name: gateway
  sleuth:
    baggage:
      remote-fields: principal
    log:
      slf4j:
        whitelisted-mdc-keys:
          - principal

sleuth_source_span.java

Span currentSpan = tracer.currentSpan();
String baggageKey = "principal";
String baggageValue = jwtVerifier.getSubjectId(token); // any value is okay
BaggageField baggageField = BaggageField.create(baggageKey);
baggageField.updateValue(currentSpan.context(), baggageValue);
try(Tracer.SpanInScope ws = tracer.withSpanInScope(currentSpan))
{
  // currentSpan.tag(baggageKey, baggageValue); // Tried both
  Tags.BAGGAGE_FIELD.tag(baggageField, currentSpan);
}
finally {
  currentSpan.finish();
}