The cargo feature set is derived from Kconfig (CONFIG_APPELFLOADER_ELF_BINFMT selects the `binfmt` feature), but the archive only depended on the Rust sources. Toggling that symbol therefore left the previously built archive in place, and the link failed on the binfmt entry points that glue/shim.c had just started referencing: appelfloader.o: in function `binfmt_load': undefined reference to `elfrs_binfmt_load' Add $(UK_CONFIG) as a prerequisite so any Kconfig change re-runs cargo, which then does its own up-to-date check.