diff --git a/src/irmin-pack/unix/io.ml b/src/irmin-pack/unix/io.ml
index 48c2afd60e..8dcf2fb8a0 100644
--- a/src/irmin-pack/unix/io.ml
+++ b/src/irmin-pack/unix/io.ml
@@ -290,4 +290,14 @@ module Unix = struct
       Sys.remove path;
       Ok ()
     with Sys_error msg -> Error (`Sys_error msg)
+
+  let fsync_dir path =
+    try
+      let dirfd =
+        Unix.openfile path Unix.[ O_RDONLY; O_SYNC; O_RSYNC ] default_open_perm
+      in
+      Unix.fsync dirfd;
+      Unix.close dirfd;
+      Ok ()
+    with Unix.Unix_error (e, s1, s2) -> Error (`Io_misc (e, s1, s2))
 end
diff --git a/src/irmin-pack/unix/io_intf.ml b/src/irmin-pack/unix/io_intf.ml
index 07b41802b3..0520984d07 100644
--- a/src/irmin-pack/unix/io_intf.ml
+++ b/src/irmin-pack/unix/io_intf.ml
@@ -143,6 +143,11 @@ module type S = sig
 
   val catch_misc_error :
     (unit -> 'a) -> ('a, [> `Io_misc of misc_error ]) result
+
+  val fsync_dir : string -> (unit, [> `Io_misc of misc_error ]) result
+  (** [fsync path] persists to the file system the directory in [path]. Note
+      that separate fsyncs are needed for persisting the files in the directory
+      [path]. *)
 end
 
 module type Sigs = sig