diff --git a/yt_dlp/networking/_requests.py b/yt_dlp/networking/_requests.py
index 2927ea7ffb..555c21ac33 100644
--- a/yt_dlp/networking/_requests.py
+++ b/yt_dlp/networking/_requests.py
@@ -143,7 +143,9 @@ class RequestsResponseAdapter(Response):
             # Work around issue with `.read(amt)` then `.read()`
             # See: https://github.com/urllib3/urllib3/issues/3636
             if amt is None:
-                amt = (1 << 31) - 1
+                # Python 3.9 preallocates the whole read buffer, read in chunks
+                read_chunk = functools.partial(self.fp.read, 1 << 20, decode_content=True)
+                return b''.join(iter(read_chunk, b''))
             # Interact with urllib3 response directly.
             return self.fp.read(amt, decode_content=True)