diff --git a/copyparty/__version__.py b/copyparty/__version__.py
index c67474ac..4be8d44f 100644
--- a/copyparty/__version__.py
+++ b/copyparty/__version__.py
@@ -1,6 +1,6 @@
 # coding: utf-8
 
-VERSION = (0, 6, 1)
+VERSION = (0, 6, 2)
 CODENAME = "CHRISTMAAAAAS"
 BUILD_DT = (2020, 12, 14)
 
diff --git a/copyparty/httpcli.py b/copyparty/httpcli.py
index 248901a4..a3c01e40 100644
--- a/copyparty/httpcli.py
+++ b/copyparty/httpcli.py
@@ -583,7 +583,7 @@ class HttpCli(object):
                     fdir = ""
 
                 try:
-                    with ren_open(fname, "wb", **open_args) as f:
+                    with ren_open(fname, "wb", 512 * 1024, **open_args) as f:
                         f, fname = f["orz"]
                         self.log("writing to {}/{}".format(fdir, fname))
                         sz, sha512_hex, _ = hashcopy(self.conn, p_data, f)
@@ -737,7 +737,7 @@ class HttpCli(object):
         if p_field != "body":
             raise Pebkac(400, "expected body, got {}".format(p_field))
 
-        with open(fp, "wb") as f:
+        with open(fp, "wb", 512 * 1024) as f:
             sz, sha512, _ = hashcopy(self.conn, p_data, f)
 
         new_lastmod = os.stat(fsenc(fp)).st_mtime
diff --git a/copyparty/util.py b/copyparty/util.py
index f735a55b..b0d84077 100644
--- a/copyparty/util.py
+++ b/copyparty/util.py
@@ -99,12 +99,15 @@ class Unrecv(object):
 
 
 @contextlib.contextmanager
-def ren_open(fname, *args, fdir=None, suffix=None, **kwargs):
-    if hasattr(fname, "write"):
+def ren_open(fname, *args, **kwargs):
+    fdir = kwargs.pop("fdir", None)
+    suffix = kwargs.pop("suffix", None)
+
+    if fname == os.devnull:
         with open(fname, *args, **kwargs) as f:
             yield {"orz": [f, fname]}
             return
-
+    
     orig_name = fname
     bname = fname
     ext = ""