I’ve done a number of rebuilds of guix-core.drv on that 24-core machine and AFAICS that fixes the issue! We’ll also have to use it in (guix gexp), which I’m pretty sure will fix . I’ll push this workaround if there are no objections. On the Guile side, we could maybe arrange to always have ‘define-once’ semantics for those bindings introduced at expansion time, as shown below (untested):