diff --git a/src/lib_client_base/client_context.ml b/src/lib_client_base/client_context.ml
index bd8566f47..ee2203375 100644
--- a/src/lib_client_base/client_context.ml
+++ b/src/lib_client_base/client_context.ml
@@ -49,6 +49,7 @@ class simple_printer log =
   end
 
 class type wallet = object
+  method with_lock : ( unit -> 'a Lwt.t) -> 'a Lwt.t
   method load : string -> default:'a -> 'a Data_encoding.encoding -> 'a tzresult Lwt.t
   method write : string -> 'a -> 'a Data_encoding.encoding -> unit tzresult Lwt.t
 end
@@ -95,6 +96,7 @@ class proxy_context (obj : full) = object
     'p -> 'q -> 'i -> (unit -> unit) tzresult Lwt.t = obj#call_streamed_service
   method error : type a b. (a, b) lwt_format -> a = obj#error
   method generic_json_call = obj#generic_json_call
+  method with_lock : type a. ( unit -> a Lwt.t) -> a Lwt.t = obj#with_lock
   method load : type a. string -> default:a -> a Data_encoding.encoding -> a tzresult Lwt.t = obj#load
   method log : type a. string -> (a, unit) lwt_format -> a = obj#log
   method message : type a. (a, unit) lwt_format -> a = obj#message
diff --git a/src/lib_client_base/client_context.mli b/src/lib_client_base/client_context.mli
index 0e62cdf42..2341db9fa 100644
--- a/src/lib_client_base/client_context.mli
+++ b/src/lib_client_base/client_context.mli
@@ -29,6 +29,7 @@ class type io = object
 end
 
 class type wallet = object
+  method with_lock : ( unit -> 'a Lwt.t) -> 'a  Lwt.t
   method load : string -> default:'a -> 'a Data_encoding.encoding -> 'a tzresult Lwt.t
   method write : string -> 'a -> 'a Data_encoding.encoding -> unit tzresult Lwt.t
 end
diff --git a/src/lib_client_base_unix/client_context_unix.ml b/src/lib_client_base_unix/client_context_unix.ml
index 3485b371f..68d8d80de 100644
--- a/src/lib_client_base_unix/client_context_unix.ml
+++ b/src/lib_client_base_unix/client_context_unix.ml
@@ -10,38 +10,62 @@
 open Client_context
 
 class unix_wallet ~base_dir : wallet = object (self)
-  method private filename alias_name =
-    Filename.concat
-      base_dir
-      (Str.(global_replace (regexp_string " ") "_" alias_name) ^ "s")
 
-  method load : type a. string -> default:a -> a Data_encoding.encoding -> a tzresult Lwt.t =
-    fun alias_name ~default encoding ->
-      let filename = self#filename alias_name in
-      if not (Sys.file_exists filename) then
-        return default
-      else
-        Lwt_utils_unix.Json.read_file filename
-        |> generic_trace
-          "couldn't to read the %s file" alias_name >>=? fun json ->
-        match Data_encoding.Json.destruct encoding json with
-        | exception _ -> (* TODO print_error *)
-            failwith "didn't understand the %s file" alias_name
-        | data ->
-            return data
+    method private filename alias_name =
+      Filename.concat
+        base_dir
+        (Str.(global_replace (regexp_string " ") "_" alias_name) ^ "s")
 
-  method write :
-    type a. string -> a -> a Data_encoding.encoding -> unit tzresult Lwt.t =
-    fun alias_name list encoding ->
-      Lwt.catch
-        (fun () ->
-           Lwt_utils_unix.create_dir base_dir >>= fun () ->
-           let filename = self#filename alias_name in
-           let json = Data_encoding.Json.construct encoding list in
-           Lwt_utils_unix.Json.write_file filename json)
-        (fun exn -> Lwt.return (error_exn exn))
-      |> generic_trace "could not write the %s alias file." alias_name
-end
+    method with_lock : type a. ( unit -> a Lwt.t) -> a Lwt.t =
+      (fun f ->
+         let unlock fd =
+           let fd = Lwt_unix.unix_file_descr fd in
+           Unix.lockf fd Unix.F_ULOCK 0;
+           Unix.close fd
+         in
+         let lock () =
+           Lwt_unix.openfile (Filename.concat base_dir "wallet_lock") 
+             Lwt_unix.[O_CREAT; O_WRONLY] 0o644 >>= fun fd ->
+           Lwt_unix.lockf fd Unix.F_LOCK 0 >>= fun () ->
+           Lwt.return (fd,(Lwt_unix.on_signal Sys.sigint
+                             (fun _s ->
+                                unlock fd;
+                                exit 0 (* exit code? *)  )))
+         in
+         lock () >>= fun (fd,sh) ->
+         (* catch might be useless if f always uses the error monad *)
+         Lwt.catch f  (function e -> Lwt.return (unlock fd; raise e))  >>= fun res ->
+         Lwt.return (unlock fd) >>= fun () ->
+         Lwt_unix.disable_signal_handler sh;
+         Lwt.return res)
+
+    method load : type a. string -> default:a -> a Data_encoding.encoding -> a tzresult Lwt.t =
+      fun alias_name ~default encoding ->
+        let filename = self#filename alias_name in
+        if not (Sys.file_exists filename) then
+          return default
+        else
+          Lwt_utils_unix.Json.read_file filename
+          |> generic_trace
+            "could not read the %s alias file" alias_name >>=? fun json ->
+          match Data_encoding.Json.destruct encoding json with
+          | exception _ -> (* TODO print_error *)
+              failwith "did not understand the %s alias file" alias_name
+          | data ->
+              return data
+
+    method write :
+      type a. string -> a -> a Data_encoding.encoding -> unit tzresult Lwt.t =
+      fun alias_name list encoding ->
+        Lwt.catch
+          (fun () ->
+             Lwt_utils_unix.create_dir base_dir >>= fun () ->
+             let filename = self#filename alias_name in
+             let json = Data_encoding.Json.construct encoding list in
+             Lwt_utils_unix.Json.write_file filename json)
+          (fun exn -> Lwt.return (error_exn exn))
+        |> generic_trace "could not write the %s alias file." alias_name
+  end
 
 class unix_prompter = object
   method prompt : type a. (a, string tzresult) lwt_format -> a =