hyperledger/fabric · error

could not unmarshal key %s to %T

Error message

could not unmarshal key %s to %T

What it means

Returned by Serializer.DeserializeFieldAsProto when proto.Unmarshal fails on the bytes fetched for a proto-typed field. The state bytes were retrieved and were []byte-typed, but do not decode into the target message — corrupt or wrong-version data.

Source

Thrown at core/chaincode/lifecycle/serializer.go:453

	}
	if value.Type == nil {
		return nil, nil
	}
	oneOf, ok := value.Type.(*lb.StateData_Bytes)
	if !ok {
		return nil, errors.Errorf("expected key %s to encode a value of type []byte, but was %T", FieldKey(namespace, name, field), value.Type)
	}
	return oneOf.Bytes, nil
}

func (s *Serializer) DeserializeFieldAsProto(namespace, name, field string, state ReadableState, msg proto.Message) error {
	bin, err := s.DeserializeFieldAsBytes(namespace, name, field, state)
	if err != nil {
		return err
	}
	err = proto.Unmarshal(bin, msg)
	if err != nil {
		return errors.Wrapf(err, "could not unmarshal key %s to %T", FieldKey(namespace, name, field), msg)
	}
	return nil
}

func (s *Serializer) DeserializeFieldAsInt64(namespace, name, field string, state ReadableState) (int64, error) {
	value, err := s.DeserializeField(namespace, name, field, state)
	if err != nil {
		return 0, err
	}
	if value.Type == nil {
		return 0, nil
	}
	oneOf, ok := value.Type.(*lb.StateData_Int64)
	if !ok {
		return 0, errors.Errorf("expected key %s to encode a value of type Int64, but was %T", FieldKey(namespace, name, field), value.Type)
	}
	return oneOf.Int64, nil
}

View on GitHub (pinned to 2736b63f8f)

Solutions

1. Verify the expected proto type matches what was serialized at that key
2. Re-commit the definition so the field is written with the correct proto payload

When it happens

Trigger: Thrown at core/chaincode/lifecycle/serializer.go:453 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of hyperledger/fabric@2736b63f8f (2026-09-04). Data as JSON: /api/errors/602703b3bf8549fe. Report an issue: GitHub.