diff --git a/pkgs/development/ocaml-modules/piaf/default.nix b/pkgs/development/ocaml-modules/piaf/default.nix
index 0d0ec1594d40..7239a70a0b74 100644
--- a/pkgs/development/ocaml-modules/piaf/default.nix
+++ b/pkgs/development/ocaml-modules/piaf/default.nix
@@ -1,5 +1,6 @@
 { alcotest-lwt
 , buildDunePackage
+, ocaml
 , dune-site
 , fetchzip
 , gluten-lwt-unix
@@ -14,6 +15,9 @@
 , uri
 }:
 
+lib.throwIf (lib.versionAtLeast ocaml.version "5.0")
+  "piaf is not available for OCaml ${ocaml.version}"
+
 buildDunePackage rec {
   pname = "piaf";
   version = "0.1.0";