diff --git a/contrib/python3-whitelist b/contrib/python3-whitelist
--- a/contrib/python3-whitelist
+++ b/contrib/python3-whitelist
@@ -352,6 +352,7 @@ test-lfconvert.t
 test-lfs-bundle.t
 test-lfs-largefiles.t
 test-lfs-pointer.py
+test-lfs-test-server.t
 test-lfs.t
 test-linelog.py
 test-linerange.py
diff --git a/hgext/lfs/blobstore.py b/hgext/lfs/blobstore.py
--- a/hgext/lfs/blobstore.py
+++ b/hgext/lfs/blobstore.py
@@ -428,6 +428,7 @@ class _gitlfsremote(object):
             request.data = filewithprogress(localstore.open(oid), None)
             request.get_method = lambda: r'PUT'
             request.add_header(r'Content-Type', r'application/octet-stream')
+            request.add_header(r'Content-Length', len(request.data))
 
         for k, v in headers:
             request.add_header(pycompat.strurl(k), pycompat.strurl(v))