diff --git a/pkgs/development/ocaml-modules/uucp/default.nix b/pkgs/development/ocaml-modules/uucp/default.nix
index 433e3f9cb106..bb70ff6a4b7e 100644
--- a/pkgs/development/ocaml-modules/uucp/default.nix
+++ b/pkgs/development/ocaml-modules/uucp/default.nix
@@ -8,8 +8,9 @@ let
   doCheck = true;
 in
 
-assert lib.assertMsg (lib.versionAtLeast ocaml.version minimumOCamlVersion)
-  "${pname} needs at least OCaml ${minimumOCamlVersion}";
+if !(lib.versionAtLeast ocaml.version minimumOCamlVersion)
+then builtins.throw "${pname} needs at least OCaml ${minimumOCamlVersion}"
+else
 
 stdenv.mkDerivation {