$upstream_response_time - value can't be parsed

[Nereis]

Following
#274
#267

We setup the following log format

upstream_response_time=\"$upstream_response_time\"

but we saw in the log we still have the following error

2024-10-02T09:57:05.910+0200        error        prometheus-nginxlog-exporter/main.go:356        error while parsing $upstream_response_time: value '"0.004"' could not be parsed into float

We are in 1.11.0.

I opened a bug but I'm not sure if I missed something in the configuration.