diff --git a/pkgs/by-name/re/red/package.nix b/pkgs/by-name/re/red/package.nix
index 38b84f4f1699..67d193c25ad4 100644
--- a/pkgs/by-name/re/red/package.nix
+++ b/pkgs/by-name/re/red/package.nix
@@ -20,6 +20,7 @@ stdenv.mkDerivation rec {
   rebol = fetchurl {
     url = "http://www.rebol.com/downloads/v278/rebol-core-278-4-2.tar.gz";
     sha256 = "1c1v0pyhf3d8z98qc93a5zmx0bbl0qq5lr8mbkdgygqsq2bv2xbz";
+    meta.license = lib.licenses.unfree; # https://www.rebol.com/license.html
   };
 
   buildInputs = [