--- a/boot/duneboot.ml
+++ b/boot/duneboot.ml
@@ -1093,7 +1093,14 @@
             `Right
               { flags =
                   (match asm.assembler with
-                   | `C_comp -> [ "-c"; fn; "-o"; out_file ]
+                   | `C_comp ->
+                     let avx512_flags =
+                       if String.is_prefix ~prefix:"blake3_avx512"
+                            (Filename.basename fn)
+                       then [ "-mavx512f"; "-mavx512vl"; "-mavx512bw" ]
+                       else []
+                     in
+                     avx512_flags @ [ "-c"; fn; "-o"; out_file ]
                    | `Msvc_asm -> [ "/nologo"; "/quiet"; "/Fo" ^ out_file; "/c"; fn ])
               ; assembler = asm.assembler
               ; out_file