diff --git a/doc/manual/src/release-notes/rl-next.md b/doc/manual/src/release-notes/rl-next.md
index 78ae99f4b..68f7d1a9d 100644
--- a/doc/manual/src/release-notes/rl-next.md
+++ b/doc/manual/src/release-notes/rl-next.md
@@ -1,2 +1,7 @@
 # Release X.Y (202?-??-??)
 
+* `<nix/fetchurl.nix>` now accepts an additional argument `impure` which
+  defaults to `false`.  If it is set to `true`, the `hash` and `sha256`
+  arguments will be ignored and the resulting derivation will have
+  `__impure` set to `true`, making it an impure derivation.
+