diff --git a/build/prefilter.ml b/build/prefilter.ml
index 3d288985c..5e48a940a 100644
--- a/build/prefilter.ml
+++ b/build/prefilter.ml
@@ -1,11 +1,11 @@
-let (major, minor, extra) =
+let (major, minor, micro, extra) =
   Scanf.sscanf Sys.ocaml_version
-    "%d.%d.%d%s" (fun j n _ s -> (j, n, s))
+    "%d.%d.%d%s" (fun j n m s -> (j, n, m, s))
 
 let filter_cookie_re =
   Str.regexp "^##V\\([<>]?=?\\)\\([^#]+\\)##"
 let version_re =
-  Str.regexp "\\([0-9]+\\)\\(\\.\\([0-9]+\\)\\)?"
+  Str.regexp "\\([0-9]+\\)\\(\\.\\([0-9]+\\)\\)?\\(\\.\\([0-9]+\\)\\)?"
 
 (* We track line count in the input source, to print location
    directives for the OCaml lexer:
@@ -57,7 +57,8 @@ let rec process_line loc line =
       if Str.string_match version_re ver_string 0 then
         let ver_maj = int_of_string (Str.matched_group 1 ver_string) in
         let ver_min = try int_of_string (Str.matched_group 3 ver_string) with _ -> 0 in
-        cmp (major*100+minor) (ver_maj*100+ver_min)
+        let ver_mic = try int_of_string (Str.matched_group 5 ver_string) with _ -> 0 in
+        cmp (major*10000+minor*100+micro) (ver_maj*10000+ver_min*100+ver_mic)
       else if ver_string = "multicore" then
         cmp (if has_domains ~extra then 5 else major) 5
       else
diff --git a/src/batMarshal.mli b/src/batMarshal.mli
index 02ef015f5..5fd3c2b32 100644
--- a/src/batMarshal.mli
+++ b/src/batMarshal.mli
@@ -60,7 +60,7 @@ type extern_flags = Marshal.extern_flags =
     No_sharing                          (** Don't preserve sharing *)
   | Closures                            (** Send function closures *)
 ##V>=4.1##  | Compat_32                           (** Ensure 32-bit compatibility *)
-##V>=5.1##  | Compression                         (** Compress the output if possible *)
+##V>=5.1####V<5.1.1##  | Compression              (** Compress the output if possible *)
 (** The flags to the [Marshal.to_*] functions below. *)
 
 
@@ -101,7 +101,7 @@ val output: _ BatInnerIO.output -> ?sharing:bool -> ?closures:bool -> 'a -> unit
    @since 2.3.0
 *)
 
-##V>=5.1##val compression_supported : unit -> bool
+##V>=5.1####V<5.1.1##val compression_supported : unit -> bool
 
 external to_string :
   'a -> extern_flags list -> string = "caml_output_value_to_string"