diff --git a/lib/uring/include/discover.ml b/lib/uring/include/discover.ml
index 9592598..732b015 100644
--- a/lib/uring/include/discover.ml
+++ b/lib/uring/include/discover.ml
@@ -31,7 +31,6 @@ let toplevel_defs c =
       "O_PATH", Int;
       "O_TMPFILE", Int;
 
-      "AT_FDCWD", Int;
       "IOV_MAX", Int;
 
       "sizeof(struct iovec)", Int;
diff --git a/lib/uring/uring.ml b/lib/uring/uring.ml
index ae5124d..6de8d1d 100644
--- a/lib/uring/uring.ml
+++ b/lib/uring/uring.ml
@@ -328,17 +328,17 @@ module Uring = struct
   external submit_readv_fixed : t -> Unix.file_descr -> id -> Cstruct.buffer -> int -> int -> offset -> bool = "ocaml_uring_submit_readv_fixed_byte" "ocaml_uring_submit_readv_fixed_native" [@@noalloc]
   external submit_writev_fixed : t -> Unix.file_descr -> id -> Cstruct.buffer -> int -> int -> offset -> bool = "ocaml_uring_submit_writev_fixed_byte" "ocaml_uring_submit_writev_fixed_native" [@@noalloc]
   external submit_close : t -> Unix.file_descr -> id -> bool = "ocaml_uring_submit_close" [@@noalloc]
-  external submit_statx : t -> id -> Unix.file_descr -> Statx.t -> Sketch.ptr -> int -> int -> bool = "ocaml_uring_submit_statx_byte" "ocaml_uring_submit_statx_native" [@@noalloc]
+  external submit_statx : t -> id -> Unix.file_descr option -> Statx.t -> Sketch.ptr -> int -> int -> bool = "ocaml_uring_submit_statx_byte" "ocaml_uring_submit_statx_native" [@@noalloc]
   external submit_splice : t -> id -> Unix.file_descr -> Unix.file_descr -> int -> bool = "ocaml_uring_submit_splice" [@@noalloc]
   external submit_bind : t -> id -> Unix.file_descr -> Sockaddr.t -> bool = "ocaml_uring_submit_bind" [@@noalloc]
   external submit_listen : t -> id -> Unix.file_descr -> int -> bool = "ocaml_uring_submit_listen" [@@noalloc]
   external submit_connect : t -> id -> Unix.file_descr -> Sockaddr.t -> bool = "ocaml_uring_submit_connect" [@@noalloc]
   external submit_accept : t -> id -> Unix.file_descr -> Sockaddr.t -> bool = "ocaml_uring_submit_accept" [@@noalloc]
   external submit_cancel : t -> id -> id -> bool = "ocaml_uring_submit_cancel" [@@noalloc]
-  external submit_openat2 : t -> id -> Unix.file_descr -> Open_how.t -> bool = "ocaml_uring_submit_openat2" [@@noalloc]
-  external submit_linkat : t -> id -> Unix.file_descr -> Sketch.ptr -> Unix.file_descr -> Sketch.ptr -> int -> bool = "ocaml_uring_submit_linkat_byte" "ocaml_uring_submit_linkat_native" [@@noalloc]
-  external submit_unlinkat : t -> id -> Unix.file_descr -> Sketch.ptr -> bool -> bool = "ocaml_uring_submit_unlinkat" [@@noalloc]
-  external submit_mkdirat : t -> id -> Unix.file_descr -> Sketch.ptr -> int -> bool = "ocaml_uring_submit_mkdirat" [@@noalloc]
+  external submit_openat2 : t -> id -> Unix.file_descr option -> Open_how.t -> bool = "ocaml_uring_submit_openat2" [@@noalloc]
+  external submit_linkat : t -> id -> Unix.file_descr option -> Sketch.ptr -> Unix.file_descr option -> Sketch.ptr -> int -> bool = "ocaml_uring_submit_linkat_byte" "ocaml_uring_submit_linkat_native" [@@noalloc]
+  external submit_unlinkat : t -> id -> Unix.file_descr option -> Sketch.ptr -> bool -> bool = "ocaml_uring_submit_unlinkat" [@@noalloc]
+  external submit_mkdirat : t -> id -> Unix.file_descr option -> Sketch.ptr -> int -> bool = "ocaml_uring_submit_mkdirat" [@@noalloc]
   external submit_send_msg : t -> id -> Unix.file_descr -> Msghdr.t -> Sketch.ptr -> bool = "ocaml_uring_submit_send_msg" [@@noalloc]
   external submit_recv_msg : t -> id -> Unix.file_descr -> Msghdr.t -> Sketch.ptr -> bool = "ocaml_uring_submit_recv_msg" [@@noalloc]
   external submit_fsync : t -> id -> Unix.file_descr -> int64 -> int -> bool = "ocaml_uring_submit_fsync" [@@noalloc]
@@ -465,9 +465,7 @@ let timeout ?(absolute = false) t clock timeout_ns user_data =
   set_timespec timespec_ptr timeout_ns;
   with_id t (fun id -> Uring.submit_timeout t.uring id timespec_ptr clock absolute) user_data
 
-let at_fdcwd : Unix.file_descr = Obj.magic Config.at_fdcwd
-
-let openat2 t ~access ~flags ~perm ~resolve ?(fd=at_fdcwd) path user_data =
+let openat2 t ~access ~flags ~perm ~resolve ?fd path user_data =
   let open_flags = flags lor match access with
     | `R  -> Open_flags.rdonly
     | `W  -> Open_flags.wronly
@@ -482,20 +480,20 @@ module Linkat_flags = struct
   let symlink_follow  = Config.At.symlink_follow
 end
 
-let linkat t ?(old_dir_fd=at_fdcwd) ?(new_dir_fd=at_fdcwd) ~flags ~old_path ~new_path user_data =
+let linkat t ?old_dir_fd ?new_dir_fd ~flags ~old_path ~new_path user_data =
   with_id t (fun id ->
     let old_path_buf = Sketch.String.alloc t.sketch old_path in
     let new_path_buf = Sketch.String.alloc t.sketch new_path in
     Uring.submit_linkat t.uring id old_dir_fd old_path_buf new_dir_fd new_path_buf flags
   ) user_data
 
-let unlink t ~dir ?(fd=at_fdcwd) path user_data =
+let unlink t ~dir ?fd path user_data =
   with_id t (fun id ->
       let buf = Sketch.String.alloc t.sketch path in
       Uring.submit_unlinkat t.uring id fd buf dir
     ) user_data
 
-let mkdirat t ~mode ?(fd=at_fdcwd) path user_data =
+let mkdirat t ~mode ?fd path user_data =
   with_id t (fun id ->
       let buf = Sketch.String.alloc t.sketch path in
       Uring.submit_mkdirat t.uring id fd buf mode
@@ -541,7 +539,7 @@ let poll_add t fd poll_mask user_data =
 let close t fd user_data =
   with_id t (fun id -> Uring.submit_close t.uring fd id) user_data
 
-let statx t ?(fd=at_fdcwd) ~mask path statx flags user_data =
+let statx t ?fd ~mask path statx flags user_data =
   let spath = Sketch.String.alloc t.sketch path in
   with_id_full t (fun id -> Uring.submit_statx t.uring id fd statx spath flags mask) user_data ~extra_data:statx
 
diff --git a/lib/uring/uring_stubs.c b/lib/uring/uring_stubs.c
index 3ae351a..2368d1e 100644
--- a/lib/uring/uring_stubs.c
+++ b/lib/uring/uring_stubs.c
@@ -242,6 +242,14 @@ ocaml_uring_make_open_how(value v_flags, value v_mode, value v_resolve, value v_
   CAMLreturn(v);
 }
 
+static int with_at_fdcwd(value v_fd)
+{
+  if (Is_none(v_fd))
+    return AT_FDCWD;
+  else
+    return Int_val(Some_val(v_fd));
+}
+
 // Caller must ensure v_open_how is not GC'd until the job is finished.
 value /* noalloc */
 ocaml_uring_submit_openat2(value v_uring, value v_id, value v_fd, value v_open_how) {
@@ -249,7 +257,7 @@ ocaml_uring_submit_openat2(value v_uring, value v_id, value v_fd, value v_open_h
   struct io_uring_sqe *sqe = io_uring_get_sqe(ring);
   if (!sqe) return (Val_false);
   struct open_how_data *data = Open_how_val(v_open_how);
-  io_uring_prep_openat2(sqe, Int_val(v_fd), data->path, &data->how);
+  io_uring_prep_openat2(sqe, with_at_fdcwd(v_fd), data->path, &data->how);
   io_uring_sqe_set_data(sqe, (void *)Long_val(v_id));
   return (Val_true);
 }
@@ -483,7 +491,7 @@ ocaml_uring_submit_statx_native(value v_uring, value v_id, value v_fd, value v_s
   struct io_uring_sqe *sqe = io_uring_get_sqe(ring);
   if (!sqe) return (Val_false);
   char *path = Sketch_ptr_val(v_sketch_ptr);
-  io_uring_prep_statx(sqe, Int_val(v_fd), path, Int_val(v_flags), Int_val(v_mask), Statx_val(v_statx));
+  io_uring_prep_statx(sqe, with_at_fdcwd(v_fd), path, Int_val(v_flags), Int_val(v_mask), Statx_val(v_statx));
   io_uring_sqe_set_data(sqe, (void *)Long_val(v_id));
   return (Val_true);
 }
@@ -873,7 +881,7 @@ ocaml_uring_submit_unlinkat(value v_uring, value v_id, value v_fd, value v_sketc
   int flags = Bool_val(v_rmdir) ? AT_REMOVEDIR : 0;
   char *path = Sketch_ptr_val(v_sketch_ptr);
   if (!sqe) return (Val_false);
-  io_uring_prep_unlinkat(sqe, Int_val(v_fd), path, flags);
+  io_uring_prep_unlinkat(sqe, with_at_fdcwd(v_fd), path, flags);
   io_uring_sqe_set_data(sqe, (void *)Long_val(v_id));
   return (Val_true);
 }
@@ -884,7 +892,7 @@ ocaml_uring_submit_mkdirat(value v_uring, value v_id, value v_fd, value v_sketch
   struct io_uring_sqe *sqe = io_uring_get_sqe(ring);
   char *path = Sketch_ptr_val(v_sketch_ptr);
   if (!sqe) return (Val_false);
-  io_uring_prep_mkdirat(sqe, Int_val(v_fd), path, Int_val(v_mode));
+  io_uring_prep_mkdirat(sqe, with_at_fdcwd(v_fd), path, Int_val(v_mode));
   io_uring_sqe_set_data(sqe, (void *)Long_val(v_id));
   return (Val_true);
 }
@@ -1097,7 +1105,7 @@ ocaml_uring_submit_linkat_native(value v_uring, value v_id,
   if (!sqe)
     return Val_false;
 
-  io_uring_prep_linkat(sqe, Int_val(v_old_dir), old_path, Int_val(v_new_dir), new_path, Int_val(v_flags));
+  io_uring_prep_linkat(sqe, with_at_fdcwd(v_old_dir), old_path, with_at_fdcwd(v_new_dir), new_path, Int_val(v_flags));
   io_uring_sqe_set_data(sqe, (void *)Long_val(v_id));
 
   return Val_true;