diff --git a/stdlib/hashtbl.mli b/stdlib/hashtbl.mli
index f67b6711d..f804d2a38 100644
--- a/stdlib/hashtbl.mli
+++ b/stdlib/hashtbl.mli
@@ -195,10 +195,26 @@ val randomize : unit -> unit
     @since 4.00.0 *)
 
 val is_randomized : unit -> bool
-(** return if the tables are currently created in randomized mode by default
-
+(** Return [true] if the tables are currently created in randomized mode
+     by default, [false] otherwise.
     @since 4.03.0 *)
 
+val rebuild : ?random (* thwart tools/unlabel *) :bool -> ('a, 'b) t -> ('a, 'b) t
+(** Return a copy of the given hashtable.  Unlike {!copy},
+    [{!rebuild} h] re-hashes all the (key, value) entries of
+    the original table [h].  The returned hash table is randomized if
+    [h] was randomized, or the optional [random] parameter is true, or
+    if the default is to create randomized hash tables; see
+    {!create} for more information.
+
+    {!rebuild} can safely be used to import a hash table built
+    by an old version of the {!Hashtbl} module, then marshaled to
+    persistent storage.  After unmarshaling, apply {!rebuild}
+    to produce a hash table for the current version of the {!Hashtbl}
+    module.
+
+    @since 4.12.0 *)
+
 (** @since 4.00.0 *)
 type statistics = {
   num_bindings: int;
diff --git a/stdlib/moreLabels.mli b/stdlib/moreLabels.mli
index fd4b088e8..849409222 100644
--- a/stdlib/moreLabels.mli
+++ b/stdlib/moreLabels.mli
@@ -206,10 +206,26 @@ val randomize : unit -> unit
     @since 4.00.0 *)
 
 val is_randomized : unit -> bool
-(** return if the tables are currently created in randomized mode by default
-
+(** Return [true] if the tables are currently created in randomized mode
+     by default, [false] otherwise.
     @since 4.03.0 *)
 
+val rebuild : ?random (* thwart tools/unlabel *) :bool -> ('a, 'b) t -> ('a, 'b) t
+(** Return a copy of the given hashtable.  Unlike {!copy},
+    [{!rebuild} h] re-hashes all the (key, value) entries of
+    the original table [h].  The returned hash table is randomized if
+    [h] was randomized, or the optional [random] parameter is true, or
+    if the default is to create randomized hash tables; see
+    {!create} for more information.
+
+    {!rebuild} can safely be used to import a hash table built
+    by an old version of the {!Hashtbl} module, then marshaled to
+    persistent storage.  After unmarshaling, apply {!rebuild}
+    to produce a hash table for the current version of the {!Hashtbl}
+    module.
+
+    @since 4.12.0 *)
+
 (** @since 4.00.0 *)
 type statistics = Hashtbl.statistics = {
   num_bindings: int;
diff --git a/stdlib/templates/hashtbl.template.mli b/stdlib/templates/hashtbl.template.mli
index d2d0f424e..474a0d023 100644
--- a/stdlib/templates/hashtbl.template.mli
+++ b/stdlib/templates/hashtbl.template.mli
@@ -195,10 +195,26 @@ val randomize : unit -> unit
     @since 4.00.0 *)
 
 val is_randomized : unit -> bool
-(** return if the tables are currently created in randomized mode by default
-
+(** Return [true] if the tables are currently created in randomized mode
+     by default, [false] otherwise.
     @since 4.03.0 *)
 
+val rebuild : ?random (* thwart tools/unlabel *) :bool -> ('a, 'b) t -> ('a, 'b) t
+(** Return a copy of the given hashtable.  Unlike {!copy},
+    [{!rebuild} h] re-hashes all the (key, value) entries of
+    the original table [h].  The returned hash table is randomized if
+    [h] was randomized, or the optional [random] parameter is true, or
+    if the default is to create randomized hash tables; see
+    {!create} for more information.
+
+    {!rebuild} can safely be used to import a hash table built
+    by an old version of the {!Hashtbl} module, then marshaled to
+    persistent storage.  After unmarshaling, apply {!rebuild}
+    to produce a hash table for the current version of the {!Hashtbl}
+    module.
+
+    @since 4.12.0 *)
+
 (** @since 4.00.0 *)
 type statistics = {
   num_bindings: int;