diff --git a/pkgs/games/unnethack/default.nix b/pkgs/games/unnethack/default.nix
index af402a7de9359..f328b8c01eed7 100644
--- a/pkgs/games/unnethack/default.nix
+++ b/pkgs/games/unnethack/default.nix
@@ -33,6 +33,11 @@ stdenv.mkDerivation rec {
     })
   ];
 
+  # Fails at startup due to off-by-one:
+  #   https://github.com/NixOS/nixpkgs/issues/292113#issuecomment-1969989058
+  # TODO: drop it once 6.x branch releases.
+  hardeningDisable = [ "fortify3" ];
+
   # Fails the build occasionally due to missing buid depends:
   #   ./../sys/unix/unixmain.c:9:10: fatal error: date.h: No such file or directory
   # TODO: remove once upstream issue is fixed: