HTTPBlueprint POST files path

I’m using the HTTPBlueprint plugin to interact with an LLM server and with a Speech-to-Text server based on whisper.cpp. I have created an Audio Capture blueprint that records and saves the recording into a WAV file. I know the whisper.cpp server works since it transcribes the WAV file when passing it via terminal with:

curl http://[WHISPER-SERVER]:PORT/inference -F file=“PATH-TO-WAV”

I also have tested the whisper.cpp server with a simple Python script:

import requests

url = 'http://[WHISPER-SERVER]:PORT/inference'   
payload = {'file': 'PATH-TO/voice2text.wav'}
output = requests.post(url, files=payload )

I need to do the same but from inside Unreal. Below I paste the part of my Blueprint where I’m trying to use the HTTPBlueprint plugin to send a POST request without success since every time I play it, the server prints an error like this:

error: no ‘file’ field in the request