diff --git a/guix/build/syscalls.scm b/guix/build/syscalls.scm
index f8c9937f54..960339e8bf 100644
--- a/guix/build/syscalls.scm
+++ b/guix/build/syscalls.scm
@@ -793,20 +793,24 @@ (define kexec-load-file
                                          unsigned-long    ;cmdline length
                                          '*               ;cmdline
                                          unsigned-long))) ;flags
-         ;; TODO: Don't do this.
          (syscall-id (match (utsname:machine (uname))
                        ("i686"    320)
                        ("x86_64"  320)
                        ("armv7l"  401)
-                       ("aarch64" 401)
-                       ;; XXX: There's apparently no support for ppc64le and
-                       ;; riscv64.
+                       ("aarch64" 294)
+                       ("ppc64le" 382)
+                       ("riscv64" 294)
                        (_ #f))))
     (lambda* (kernel-fd initrd-fd command-line #:optional (flags 0))
       "Load for eventual use of kexec(8) the Linux kernel from
 @var{kernel-fd}, its initial RAM disk from @var{initrd-fd}, with the given
 @var{command-line} (a string).  Optionally, @var{flags} can be a bitwise or of
 the KEXEC_FILE_* constants."
+      (unless syscall-id
+        (throw 'system-error "kexec-load-file" "~A"
+               (list (strerror ENOSYS))
+               (list ENOSYS)))
+
       (let*-values (((command-line)
                      (string->utf-8/nul-terminated command-line))
                     ((ret err)