diff --git a/oxenstored/connection.ml b/oxenstored/connection.ml
index 4ec2668..fc55309 100644
--- a/oxenstored/connection.ml
+++ b/oxenstored/connection.ml
@@ -317,7 +317,7 @@ let get_children_watches con path =
   let path = path ^ "/" in
   List.concat
     (Hashtbl.fold
-       (fun p w l -> if String.startswith path p then w :: l else l)
+       (fun p w l -> if String.starts_with ~prefix:path p then w :: l else l)
        con.watches []
     )
 
diff --git a/oxenstored/logging.ml b/oxenstored/logging.ml
index 29165e7..17cb1a7 100644
--- a/oxenstored/logging.ml
+++ b/oxenstored/logging.ml
@@ -25,7 +25,7 @@ let log_destination_of_string s =
   let prefix = "syslog:" in
   let len_prefix = String.length prefix in
   let len = String.length s in
-  if String.startswith prefix s then
+  if String.starts_with ~prefix s then
     Syslog
       (Syslog.facility_of_string (String.sub s len_prefix (len - len_prefix)))
   else
@@ -435,7 +435,7 @@ let live_update () =
 let xb_answer ~tid ~con ~ty data =
   let print, level =
     match ty with
-    | Xenbus.Xb.Op.Error when String.startswith "ENOENT" data ->
+    | Xenbus.Xb.Op.Error when String.starts_with ~prefix:"ENOENT" data ->
         (!access_log_read_ops, Warn)
     | Xenbus.Xb.Op.Error ->
         (true, Warn)
diff --git a/oxenstored/stdext.ml b/oxenstored/stdext.ml
index 4024bfa..10a4d77 100644
--- a/oxenstored/stdext.ml
+++ b/oxenstored/stdext.ml
@@ -82,18 +82,6 @@ module String = struct
       let a = String.sub s 0 i
       and b = String.sub s (i + 1) (String.length s - i - 1) in
       a :: split ~limit:nlimit c b
-
-  let fold_left f accu string =
-    let accu = ref accu in
-    for i = 0 to length string - 1 do
-      accu := f !accu string.[i]
-    done ;
-    !accu
-
-  (** True if string 'x' starts with prefix 'prefix' *)
-  let startswith prefix x =
-    let x_l = String.length x and prefix_l = String.length prefix in
-    prefix_l <= x_l && String.sub x 0 prefix_l = prefix
 end
 
 module Unixext = struct