diff --git a/src/lib_base/cli_entries.ml b/src/lib_base/cli_entries.ml
index 3d04fd6ae..63b17e982 100644
--- a/src/lib_base/cli_entries.ml
+++ b/src/lib_base/cli_entries.ml
@@ -299,7 +299,7 @@ let help_group =
 
 let string_contains ~needle ~haystack =
   try
-    Some (Str.search_forward (Str.regexp_string needle) haystack 0)
+    Some Re_str.(search_forward (regexp_string needle) haystack 0)
   with Not_found ->
     None
 
@@ -615,18 +615,18 @@ let print_highlight highlight_strings formatter str =
   let rec print_string = function
     | [] -> Format.fprintf formatter "%s" str
     | regex :: tl ->
-        begin match Str.full_split regex str with
+        begin match Re_str.full_split regex str with
           | []
-          | [ Str.Text _ ] -> print_string tl
+          | [ Re_str.Text _ ] -> print_string tl
           | list ->
               List.iter
                 (function
-                  | Str.Text text -> Format.fprintf formatter "%s" text
-                  | Str.Delim delimiter ->
+                  | Re_str.Text text -> Format.fprintf formatter "%s" text
+                  | Re_str.Delim delimiter ->
                       Format.fprintf formatter "@{<hilight>%s@}" delimiter)
                 list
         end
-  in print_string (List.map Str.regexp_string highlight_strings)
+  in print_string (List.map Re_str.regexp_string highlight_strings)
 
 let print_commandline ppf (highlights, options, args) =
   let rec print
@@ -1121,7 +1121,7 @@ let autocomplete ~script ~cur_arg ~prev_arg ~args ~tree ~global_options cctxt =
           end
   end >>|? fun completions ->
   List.filter
-    (fun completion -> Str.string_match (Str.regexp_string cur_arg) completion 0)
+    (fun completion -> Re_str.(string_match (regexp_string cur_arg) completion 0))
     completions
 
 (* Try a list of commands on a list of arguments *)
diff --git a/src/lib_base/jbuild b/src/lib_base/jbuild
index 47dde2ada..c59b4c5a9 100644
--- a/src/lib_base/jbuild
+++ b/src/lib_base/jbuild
@@ -18,6 +18,7 @@
               tezos-rpc
               tezos-micheline
               tezos-protocol-environment-sigs
+              re.str
               calendar
               ezjsonm
               lwt.unix
diff --git a/src/lib_client_base/client_commands.ml b/src/lib_client_base/client_commands.ml
index dc19c848e..3214e52d6 100644
--- a/src/lib_client_base/client_commands.ml
+++ b/src/lib_client_base/client_commands.ml
@@ -91,7 +91,7 @@ class file_wallet dir : wallet = object (self)
   method private filename alias_name =
     Filename.concat
       dir
-      (Str.(global_replace (regexp_string " ") "_" alias_name) ^ "s")
+      (Re_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 ->
diff --git a/src/lib_client_base/client_keys.ml b/src/lib_client_base/client_keys.ml
index b58cf359a..e33bf035d 100644
--- a/src/lib_client_base/client_keys.ml
+++ b/src/lib_client_base/client_keys.ml
@@ -197,8 +197,8 @@ let gen_keys_containing ?(prefix=false) ?(force=false) ~containing ~name (cctxt
                      String.sub key 0 (String.length containing) = containing)
                   containing_tz1)
             else
-              let re = Str.regexp (String.concat "\\|" containing) in
-              (fun key -> try ignore (Str.search_forward re key 0); true
+              let re = Re_str.regexp (String.concat "\\|" containing) in
+              (fun key -> try ignore (Re_str.search_forward re key 0); true
                 with Not_found -> false) in
           let rec loop attempts =
             let seed = Ed25519.Seed.generate () in
diff --git a/src/proto_alpha/lib_protocol/test/test_michelson.ml b/src/proto_alpha/lib_protocol/test/test_michelson.ml
index 7d0fc1376..24bd2828a 100644
--- a/src/proto_alpha/lib_protocol/test/test_michelson.ml
+++ b/src/proto_alpha/lib_protocol/test/test_michelson.ml
@@ -55,7 +55,7 @@ let parse_execute sb ?tc code_str param_str storage_str =
 let test ctxt ?tc (file_name: string) (storage: string) (input: string) =
   let full_path = contract_path // file_name ^ ".tz" in
   let file = Helpers_misc.read_file full_path in
-  let spaced_file = Str.global_replace (Str.regexp_string "\n") "\n " file in
+  let spaced_file = Re_str.(global_replace (regexp_string "\n") "\n " file) in
   let program = "{" ^ spaced_file ^ "}" in
   parse_execute ctxt ?tc program input storage