Unexpected behaviour when processing query encoded sha1 hash

[volbil]

Hello everyone. I've stuck with a quite peculiar issue. I'm trying to implement a simple torrent announcer. Among the data it receives from torrent clients is info_hash field (urlencoded 20-byte SHA1 hash according to specs). However, when I'm trying to decode said hash in Starlette app, it returns corrupted gibberish.

Here is a proof-of-concept app to reproduce this issue:

Request: /test?info_hash=%95%DE%04%8AL%03%1C%27%A9%B3%18%DD1%B0%89%8CxFg%9C

from starlette.responses import PlainTextResponse
from starlette.applications import Starlette
from starlette.routing import Route


def test(request):
    # This outputs so hash is already corrupted at this point
    # info_hash=%EF%BF%BD%EF%BF%BD%04%EF%BF%BDL%03%1C%27%EF%BF%BD%EF%BF%BD%18%EF%BF%BD1%EF%BF%BD%EF%BF%BD%EF%BF%BDxFg%EF%BF%BD
    print(request.query_params)

    # Plain text response is some unintelligible characters
    return PlainTextResponse(request.query_params["info_hash"])


routes = [Route("/test", test)]

app = Starlette(debug=True, routes=routes)

I've managed to properly decode info_hash using this approach:

from urllib.parse import unquote_to_bytes

# This returns correct hash: 95de048a4c031c27a9b318dd31b0898c7846679c
unquote_to_bytes("%95%DE%04%8AL%03%1C%27%A9%B3%18%DD1%B0%89%8CxFg%9C").hex()

After some digging, I located the code where corruption most likely happens:
https://github.com/encode/starlette/blob/master/starlette/datastructures.py#L414-L416

I've already spent an unhealthy amount of time trying to solve this so I would appreciate any help on this issue.