Hi, Regardless of my last email, I've now committed a minor change to expl3 repository by which all of \let:NN, \glet:NN, \let_new:NN, and \glet_new:NN are defined with \def_protected_long_new, and the variants are plain old \def_new. (No change, then, to \let:NN at all. Just bringing the others into line.) The only real change this makes that I'm aware of is that \let_new:NN \par \foo will now complain '\par already defined' rather than 'runaway argument'. I think this is sensible since \let:NN itself does allow \par. Let me know if I've missed something :) Cheers, Will