diff --git a/pkgs/development/libraries/opencascade/6.5.nix b/pkgs/development/libraries/opencascade/6.5.nix
index 4228c285dfd5..a1143757c77e 100644
--- a/pkgs/development/libraries/opencascade/6.5.nix
+++ b/pkgs/development/libraries/opencascade/6.5.nix
@@ -26,6 +26,8 @@ stdenv.mkDerivation rec {
   # https://bugs.freedesktop.org/show_bug.cgi?id=83631
     + " -DGLX_GLXEXT_LEGACY";
 
+  hardening_format = false;
+
   configureFlags = [ "--with-tcl=${tcl}/lib" "--with-tk=${tk}/lib" "--with-qt=${qt4}" "--with-ftgl=${ftgl}" "--with-freetype=${freetype}" ];
 
   postInstall = ''