diff --git a/src/proto_alpha/lib_baking/client_baking_nonces.ml b/src/proto_alpha/lib_baking/client_baking_nonces.ml
index 8ea902e64..4daa8ad33 100644
--- a/src/proto_alpha/lib_baking/client_baking_nonces.ml
+++ b/src/proto_alpha/lib_baking/client_baking_nonces.ml
@@ -10,7 +10,6 @@
 open Proto_alpha
 open Alpha_context
 
-(* TODO locking... *)
 
 type t = (Block_hash.t * Nonce.t) list
 
@@ -28,29 +27,36 @@ let load (wallet : #Client_context.wallet) =
   wallet#load ~default:[] name encoding
 
 let save (wallet : #Client_context.wallet) list =
-  wallet#write name list encoding
+  wallet#with_lock (fun () ->
+      wallet#write name list encoding)
 
 let mem (wallet : #Client_context.wallet) block_hash =
-  load wallet >>|? fun data ->
-  List.mem_assoc block_hash data
+  wallet#with_lock (fun () ->
+      load wallet >>|? fun data ->
+      List.mem_assoc block_hash data)
 
-let find wallet block_hash =
-  load wallet >>|? fun data ->
-  try Some (List.assoc block_hash data)
-  with Not_found -> None
+let find (wallet : #Client_context.wallet) block_hash =
+  wallet#with_lock ( fun () ->
+    load wallet >>|? fun data ->
+    try Some (List.assoc block_hash data)
+    with Not_found -> None)
 
-let add wallet block_hash nonce =
+
+let add (wallet : #Client_context.wallet) block_hash nonce =
+  wallet#with_lock ( fun () ->
   load wallet >>=? fun data ->
   save wallet ((block_hash, nonce) ::
-               List.remove_assoc block_hash data)
+               List.remove_assoc block_hash data))
 
-let del wallet block_hash =
-  load wallet >>=? fun data ->
-  save wallet (List.remove_assoc block_hash data)
+let del (wallet : #Client_context.wallet) block_hash =
+  wallet#with_lock ( fun () ->
+    load wallet >>=? fun data ->
+    save wallet (List.remove_assoc block_hash data))
 
-let dels wallet hashes =
+let dels (wallet : #Client_context.wallet) hashes =
+  wallet#with_lock ( fun () ->
   load wallet >>=? fun data ->
   save wallet @@
   List.fold_left
     (fun data hash -> List.remove_assoc hash data)
-    data hashes
+    data hashes)