diff --git a/packages/ts-plugin/README.md b/packages/ts-plugin/README.md
index e5fa0f1..5815301 100644
--- a/packages/ts-plugin/README.md
+++ b/packages/ts-plugin/README.md
@@ -145,13 +145,16 @@ to this to point LSP at it:
                                 "node_modules/")))
              (lsp-dependency 'typescript-language-server
                              `(:system ,(concat node-modules
-                                                "typescript-language-server/lib/cli.js")))
+                                                "typescript-language-server/lib/cli.mjs")))
              (lsp-dependency 'typescript
                              `(:system ,(concat node-modules
                                                 "typescript/lib/tsserver.js")))))
       ))))
 ```
 
+Older versions of `typescript-language-server` use `cli.js` instead of
+`cli.mjs` above.
+
 ### Visual Studio Code
 
 After `yarn install`, if you have a `node_modules/typescript`