Submitted upstream:
https://github.com/racket/racket/pull/4703

diff --git a/racket/src/rktboot/machine-def.rkt b/racket/src/rktboot/machine-def.rkt
index 8ff0688..59ebfc8 100644
--- a/racket/src/rktboot/machine-def.rkt
+++ b/racket/src/rktboot/machine-def.rkt
@@ -25,6 +25,7 @@
                                      [(regexp-match? #rx"^t?arm32" target-machine) "arm32"]
                                      [(regexp-match? #rx"^t?arm64" target-machine) "arm64"]
                                      [(regexp-match? #rx"^t?ppc32" target-machine) "ppc32"]
+                                     [(regexp-match? #rx"^t?rv64" target-machine) "rv64"]
                                      [(regexp-match? #rx"^t?pb" target-machine) "pb"]
                                      [else (error "machine.def: cannot infer architecture")]))]
                [s (regexp-replace* #rx"[$][(]Mend[)]" s