No need to use profile hex. Proxy settings are applied globally.

src/rebar_pkg_resource.erl

@@ -95,8 +95,7 @@ make_vsn(_) ->
 request(Url, ETag) ->
     case httpc:request(get, {Url, [{"if-none-match", ETag} || ETag =/= false]},
                        [{relaxed, true}],
-                       [{body_format, binary}],
-                       hex) of
+                       [{body_format, binary}]) of
         {ok, {{_Version, 200, _Reason}, Headers, Body}} ->
             ?DEBUG("Successfully downloaded ~s", [Url]),
             {"etag", ETag1} = lists:keyfind("etag", 1, Headers),