diff --git a/README.markdown b/README.markdown
index 438aff3..82e3e59 100644
--- a/README.markdown
+++ b/README.markdown
@@ -19,6 +19,14 @@ package support:
 
 You might also want [salve.vim][] for assorted static project support.
 
+## ClojureScript
+
+When editing a `.cljs` file Fireplace needs a default ClojureScript REPL before
+it can `:EvalCljs` or send forms. Enable it as follows:
+
+- shadow-cljs: `:CljEval (shadow/repl :app)` where :app is the cljs build ID.
+- nbb: `:CljEval (ns cljs.user)` since it's already a cljs REPL by default.
+
 ## Features
 
 This list isn't exhaustive; see the `:help` for details.