Add clarification about on_new_config

1 files changed, 2 insertions, 1 deletions

diff --git a/README.md b/README.md
index f902bb0b..754d1aeb 100644
--- a/README.md
+++ b/README.md
@@ -224,7 +224,8 @@ lspconfig.SERVER.setup{config}
     `function(new_config, new_root_dir)` will be executed after a new configuration has been
     created as a result of {root_dir} returning a unique value. You can use this
     as an opportunity to further modify the new_config or use it before it is
-    sent to |vim.lsp.start_client()|.
+    sent to |vim.lsp.start_client()|. If you set a custom `on_new_config`, ensure that 
+    `new_config.cmd = cmd` is present within the function body.
 ```
 
 # Individual server documentation