diff --git a/pkgs/tools/security/cb0cat/default.nix b/pkgs/tools/security/cb0cat/default.nix
index e35434f3cc2..251c9126056 100644
--- a/pkgs/tools/security/cb0cat/default.nix
+++ b/pkgs/tools/security/cb0cat/default.nix
@@ -17,6 +17,7 @@ stdenv.mkDerivation rec {
   meta = {
     description = "cryptographic tool based on the CBEAMr0 sponge function";
     homepage    = "https://www.cblnk.com";
+    platforms   = stdenv.lib.platforms.unix;
     license     = stdenv.lib.licenses.bsd3;
     maintainers = [ stdenv.lib.maintainers.thoughtpolice ];
   };