2 files changed, 6 insertions, 1 deletions

diff --git a/src/luarocks/cfg.lua b/src/luarocks/cfg.lua
index a22cf121..e41b632c 100644
--- a/src/luarocks/cfg.lua
+++ b/src/luarocks/cfg.lua
@@ -149,7 +149,7 @@ local sys_config_file_default, home_config_file_default
 local sys_config_dir, home_config_dir
 local sys_config_ok, home_config_ok = false, false
 local extra_luarocks_module_dir
-sys_config_dir = site_config.LUAROCKS_SYSCONFDIR
+sys_config_dir = site_config.LUAROCKS_SYSCONFDIR or site_config.LUAROCKS_PREFIX
 if cfg.platforms.windows then
    cfg.home = os.getenv("APPDATA") or "c:"
    sys_config_dir = sys_config_dir or "c:/luarocks"
diff --git a/src/luarocks/command_line.lua b/src/luarocks/command_line.lua
index dbf64b9c..e1c9f492 100644
--- a/src/luarocks/command_line.lua
+++ b/src/luarocks/command_line.lua
@@ -31,12 +31,17 @@ end
 local function replace_tree(flags, args, tree)
    tree = dir.normalize(tree)
    flags["tree"] = tree
+   local added = false
    for i = 1, #args do
       if args[i]:match("%-%-tree=") then
          args[i] = "--tree="..tree
+         added = true
          break
       end
    end
+   if not added then
+      args[#args + 1] = "--tree="..tree
+   end
    path.use_tree(tree)
 end