diff --git a/prelude.ld b/prelude.ld
index 9753575..936a34b 100644
--- a/prelude.ld
+++ b/prelude.ld
@@ -192,7 +192,9 @@ fn list {
 
 fn fold {
 	"Folds a list."
+	(f as :fn, []) -> []
 	(f as :fn, xs as :list) -> fold (f, xs, f ())
+	(f as :fn, [], root) -> []
 	(f as :fn, xs as :list, root) -> loop (root, first (xs), rest (xs)) with {
 		(prev, curr, []) -> f (prev, curr)
 		(prev, curr, remaining) -> recur (
diff --git a/src/ludus.janet b/src/ludus.janet
index 4485394..b8dd543 100644
--- a/src/ludus.janet
+++ b/src/ludus.janet
@@ -52,7 +52,8 @@
 (comment
 # (do
 (def source `
-rest ([])
+fn id (x) -> x
+map (id, [])
 `)
 (def out (-> source 
  ludus