diff --git a/CHANGES.md b/CHANGES.md
index 5d765b5038b..5d9a1a072c0 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -5,9 +5,14 @@
 - **irmin-pack**
   - Add `Irmin_pack_unix.Stats.Latest_gc` which is now the parameter of GC's
     `finished` callback (#2089, @Ngoguey42)
+  - Add `Gc.oldest_live_commit` which returns the key of the commit on which the
+    latest gc was called on. (#2110, @icristescu)
 
 ### Changed
 
+- **irmin-pack**
+  - Upgraded on-disk format to version 4. (#2110, @icristescu)
+
 ### Fixed
 
 ## 3.4.2 (2022-10-06)
diff --git a/src/irmin-pack/unix/control_file.ml b/src/irmin-pack/unix/control_file.ml
index 5145f4d1a81..3d4b3dd05c0 100644
--- a/src/irmin-pack/unix/control_file.ml
+++ b/src/irmin-pack/unix/control_file.ml
@@ -20,6 +20,12 @@ include Control_file_intf
 module Plv3 = struct
   include Payload_v3
 
+  let of_bin_string = Irmin.Type.of_bin_string t |> Irmin.Type.unstage
+end
+
+module Plv4 = struct
+  include Payload_v4
+
   let of_bin_string = Irmin.Type.of_bin_string t |> Irmin.Type.unstage
   let to_bin_string = Irmin.Type.to_bin_string t |> Irmin.Type.unstage
 end
@@ -29,10 +35,11 @@ module Version = Irmin_pack.Version
 module Data (Io : Io.S) = struct
   (** Type of what's encoded in the control file. The variant tag is encoded as
       a [Version.t]. *)
-  type t = V3 of Plv3.t
+  type t = V3 of Plv3.t | V4 of Plv4.t
 
   let to_bin_string = function
-    | V3 payload -> Version.to_bin `V3 ^ Plv3.to_bin_string payload
+    | V3 _ -> assert false
+    | V4 payload -> Version.to_bin `V4 ^ Plv4.to_bin_string payload
 
   let of_bin_string s =
     let open Result_syntax in
@@ -46,6 +53,7 @@ module Data (Io : Io.S) = struct
       | None -> Error (`Unknown_major_pack_version left)
       | Some `V3 when len > Io.page_size -> Error `Corrupted_control_file
       | Some `V3 -> Ok `V3
+      | Some `V4 -> Ok `V4
       | Some (`V1 | `V2) -> assert false
     in
     match version with
@@ -53,6 +61,10 @@ module Data (Io : Io.S) = struct
         match Plv3.of_bin_string right with
         | Ok x -> Ok (V3 x)
         | Error _ -> Error `Corrupted_control_file)
+    | `V4 -> (
+        match Plv4.of_bin_string right with
+        | Ok x -> Ok (V4 x)
+        | Error _ -> Error `Corrupted_control_file)
 end
 
 module Make (Io : Io.S) = struct
@@ -61,12 +73,35 @@ module Make (Io : Io.S) = struct
 
   type t = { io : Io.t; mutable payload : Latest_payload.t }
 
+  let upgrade_v3_to_v4 (pl : Payload_v3.t) : Payload_v4.t =
+    let status =
+      match pl.status with
+      | From_v1_v2_post_upgrade x -> Payload_v4.From_v1_v2_post_upgrade x
+      | From_v3_no_gc_yet -> No_gc_yet
+      | From_v3_used_non_minimal_indexing_strategy ->
+          Used_non_minimal_indexing_strategy
+      | From_v3_gced x ->
+          Gced
+            {
+              suffix_start_offset = x.suffix_start_offset;
+              generation = x.generation;
+              oldest_live_commit_offset = x.suffix_start_offset;
+            }
+      | _ -> assert false
+    in
+    {
+      dict_end_poff = pl.dict_end_poff;
+      suffix_end_poff = pl.suffix_end_poff;
+      status;
+      upgraded_from_v3_to_v4 = true;
+    }
+
   let write io payload =
-    let s = Data.(to_bin_string (V3 payload)) in
+    let s = Data.(to_bin_string (V4 payload)) in
 
     (* The data must fit inside a single page for atomic updates of the file.
        This is only true for some file systems. This system will have to be
-       reworked for [V3]. *)
+       reworked for [V4]. *)
     assert (String.length s <= Io.page_size);
 
     Io.write_string io ~off:Int63.zero s
@@ -80,7 +115,10 @@ module Make (Io : Io.S) = struct
        If [string] is larger than a page, it either means that the file is
        corrupted or that the major version is not supported. Either way it will
        be handled by [Data.of_bin_string]. *)
-    Data.of_bin_string string
+    let+ payload = Data.of_bin_string string in
+    match payload with
+    | V4 payload -> payload
+    | V3 payload -> upgrade_v3_to_v4 payload
 
   let create_rw ~path ~overwrite payload =
     let open Result_syntax in
@@ -91,8 +129,7 @@ module Make (Io : Io.S) = struct
   let open_ ~path ~readonly =
     let open Result_syntax in
     let* io = Io.open_ ~path ~readonly in
-    let+ data = read io in
-    let payload = match data with Data.V3 payload -> payload in
+    let+ payload = read io in
     { io; payload }
 
   let close t = Io.close t.io
@@ -103,8 +140,7 @@ module Make (Io : Io.S) = struct
     let open Result_syntax in
     if not @@ Io.readonly t.io then Error `Rw_not_allowed
     else
-      let+ data = read t.io in
-      let payload = match data with Data.V3 payload -> payload in
+      let+ payload = read t.io in
       t.payload <- payload
 
   let set_payload t payload =
diff --git a/src/irmin-pack/unix/control_file_intf.ml b/src/irmin-pack/unix/control_file_intf.ml
index 643f3fdf877..7c107b7393b 100644
--- a/src/irmin-pack/unix/control_file_intf.ml
+++ b/src/irmin-pack/unix/control_file_intf.ml
@@ -103,7 +103,64 @@ module Payload_v3 = struct
       extensions *)
 end
 
-module Latest_payload = Payload_v3
+module Payload_v4 = struct
+  type gced = {
+    suffix_start_offset : int63;
+    generation : int;
+    oldest_live_commit_offset : int63;
+  }
+  [@@deriving irmin]
+  (** Similar to [from_v3_gced]. [oldest_live_commit_offset] is the commit on
+      which the latest gc was called on. *)
+
+  (** [From_v1_v2_post_upgrade] similar to [Payload_v3.From_v1_v2_post_upgrade]
+
+      [No_gc_yet] corresponds to a pack store that was created using [`V3] or
+      above. It never underwent a GC.
+
+      [Used_non_minimal_indexing_strategy] corresponds to a pack store that was
+      created using [`V3] or above. It never underwent a GC and it will never be
+      possible to GC it because entries were pushed using a non-minimal indexing
+      strategy.
+
+      [Gced] is a [`V3] or [`V4] store that was GCed at least once.
+
+      The [T*] tags are provisional tags that the binary decoder is aware of and
+      that may in the future be used to add features to the [`V3] payload. *)
+  type status =
+    | From_v1_v2_post_upgrade of Payload_v3.from_v1_v2_post_upgrade
+    | No_gc_yet
+    | Used_non_minimal_indexing_strategy
+    | Gced of gced
+    | T1
+    | T2
+    | T3
+    | T4
+    | T5
+    | T6
+    | T7
+    | T8
+    | T9
+    | T10
+    | T11
+    | T12
+    | T13
+    | T14
+    | T15
+  [@@deriving irmin]
+
+  type t = {
+    dict_end_poff : int63;
+    suffix_end_poff : int63;
+    status : status;
+    upgraded_from_v3_to_v4 : bool;
+  }
+  [@@deriving irmin]
+  (** Similar to [`V3] payload. [upgraded_from_v3_to_v4] recalls if the store
+      was originally created in [`V3]. *)
+end
+
+module Latest_payload = Payload_v4
 
 module type S = sig
   (** Abstraction for irmin-pack's control file.
@@ -192,8 +249,9 @@ module type S = sig
 end
 
 module type Sigs = sig
-  module Latest_payload = Payload_v3
+  module Latest_payload = Payload_v4
   module Payload_v3 = Payload_v3
+  module Payload_v4 = Payload_v4
 
   module type S = S
 
diff --git a/src/irmin-pack/unix/dispatcher.ml b/src/irmin-pack/unix/dispatcher.ml
index 555bbf16648..70854fd41c2 100644
--- a/src/irmin-pack/unix/dispatcher.ml
+++ b/src/irmin-pack/unix/dispatcher.ml
@@ -58,13 +58,13 @@ module Make (Fm : File_manager.S with module Io = Io.Unix) :
   let suffix_start_offset t =
     let pl = Control.payload (Fm.control t.fm) in
     match pl.status with
-    | Payload.From_v1_v2_post_upgrade _
-    | From_v3_used_non_minimal_indexing_strategy | From_v3_no_gc_yet ->
+    | Payload.From_v1_v2_post_upgrade _ | Used_non_minimal_indexing_strategy
+    | No_gc_yet ->
         Int63.zero
     | T1 | T2 | T3 | T4 | T5 | T6 | T7 | T8 | T9 | T10 | T11 | T12 | T13 | T14
     | T15 ->
         assert false
-    | From_v3_gced { suffix_start_offset; _ } -> suffix_start_offset
+    | Gced { suffix_start_offset; _ } -> suffix_start_offset
 
   (* The suffix only know the real offsets, it is in the dispatcher that global
      offsets are translated into real ones (i.e. in prefix or suffix offsets). *)
diff --git a/src/irmin-pack/unix/ext.ml b/src/irmin-pack/unix/ext.ml
index 3ffe9b5c3d1..b1910a1f3eb 100644
--- a/src/irmin-pack/unix/ext.ml
+++ b/src/irmin-pack/unix/ext.ml
@@ -250,14 +250,6 @@ module Maker (Config : Conf.S) = struct
                           (Irmin.Type.to_string XKey.t commit_key))
                   | Some (k, _kind) -> Ok k)
             in
-            let offset =
-              let state : _ Pack_key.state = Pack_key.inspect commit_key in
-              match state with
-              | Direct x ->
-                  let len = x.length |> Int63.of_int in
-                  Int63.Syntax.(x.offset + len)
-              | Indexed _ -> assert false
-            in
             let root = Conf.root t.config in
             let* () =
               if not (File_manager.gc_allowed t.fm) then Error `Gc_disallowed
@@ -266,7 +258,7 @@ module Maker (Config : Conf.S) = struct
             let current_generation = File_manager.generation t.fm in
             let next_generation = current_generation + 1 in
             let gc =
-              Gc.v ~root ~generation:next_generation ~unlink ~offset
+              Gc.v ~root ~generation:next_generation ~unlink
                 ~dispatcher:t.dispatcher ~fm:t.fm ~contents:t.contents
                 ~node:t.node ~commit:t.commit commit_key
             in
@@ -318,6 +310,31 @@ module Maker (Config : Conf.S) = struct
             | Some { use_auto_finalisation = true; _ } ->
                 let* _ = finalise_exn ~wait:false t in
                 Lwt.return_unit
+
+          let oldest_live_commit t =
+            let pl = Control.payload (File_manager.control t.fm) in
+            match pl.status with
+            | From_v1_v2_post_upgrade _ | Used_non_minimal_indexing_strategy
+            | No_gc_yet ->
+                None
+            | T1 | T2 | T3 | T4 | T5 | T6 | T7 | T8 | T9 | T10 | T11 | T12 | T13
+            | T14 | T15 ->
+                assert false
+            | Gced { oldest_live_commit_offset = offset; _ } -> (
+                let entry =
+                  Commit.CA.read_and_decode_entry_prefix ~off:offset
+                    t.dispatcher
+                in
+                match Commit.CA.Entry_prefix.total_entry_length entry with
+                | None ->
+                    (* Stores which support gc, also have a length in the header
+                       of all their entries. *)
+                    assert false
+                | Some length ->
+                    let key =
+                      Pack_key.v_direct ~offset ~length ~hash:entry.hash
+                    in
+                    Some key)
         end
 
         let batch t f =
@@ -573,6 +590,7 @@ module Maker (Config : Conf.S) = struct
 
       let is_allowed repo = File_manager.gc_allowed repo.X.Repo.fm
       let cancel repo = X.Repo.Gc.cancel repo
+      let oldest_live_commit = X.Repo.Gc.oldest_live_commit
     end
 
     module Traverse_pack_file = Traverse_pack_file.Make (struct
diff --git a/src/irmin-pack/unix/file_manager.ml b/src/irmin-pack/unix/file_manager.ml
index 55875513a2f..3690bb5f3d0 100644
--- a/src/irmin-pack/unix/file_manager.ml
+++ b/src/irmin-pack/unix/file_manager.ml
@@ -77,14 +77,14 @@ struct
     t.suffix_consumers <- { after_flush } :: t.suffix_consumers
 
   let generation = function
-    | Payload.From_v1_v2_post_upgrade _
-    | From_v3_used_non_minimal_indexing_strategy | From_v3_no_gc_yet ->
+    | Payload.From_v1_v2_post_upgrade _ | Used_non_minimal_indexing_strategy
+    | No_gc_yet ->
         0
     | T1 | T2 | T3 | T4 | T5 | T6 | T7 | T8 | T9 | T10 | T11 | T12 | T13 | T14
     | T15 ->
         (* Unreachable *)
         assert false
-    | From_v3_gced x -> x.generation
+    | Gced x -> x.generation
 
   (** Flush stages *************************************************************
 
@@ -130,17 +130,17 @@ struct
         let status =
           match pl.status with
           | From_v1_v2_post_upgrade _ -> pl.status
-          | From_v3_gced _ -> pl.status
-          | From_v3_no_gc_yet ->
+          | Gced _ -> pl.status
+          | No_gc_yet ->
               if Irmin_pack.Indexing_strategy.is_minimal t.indexing_strategy
               then pl.status
               else (
                 [%log.warn
-                  "Updating the control file from [From_v3] to \
-                   [From_v3_used_non_minimal_indexing_strategy]. It won't be \
-                   possible to GC this irmin-pack store anymore."];
-                Payload.From_v3_used_non_minimal_indexing_strategy)
-          | From_v3_used_non_minimal_indexing_strategy -> pl.status
+                  "Updating the control file to \
+                   [Used_non_minimal_indexing_strategy]. It won't be possible \
+                   to GC this irmin-pack store anymore."];
+                Payload.Used_non_minimal_indexing_strategy)
+          | Used_non_minimal_indexing_strategy -> pl.status
           | T1 | T2 | T3 | T4 | T5 | T6 | T7 | T8 | T9 | T10 | T11 | T12 | T13
           | T14 | T15 ->
               assert false
@@ -294,10 +294,10 @@ struct
     let pl : Payload.t = Control.payload control in
     let generation =
       match pl.status with
-      | From_v1_v2_post_upgrade _ | From_v3_no_gc_yet
-      | From_v3_used_non_minimal_indexing_strategy ->
+      | From_v1_v2_post_upgrade _ | No_gc_yet
+      | Used_non_minimal_indexing_strategy ->
           0
-      | From_v3_gced x -> x.generation
+      | Gced x -> x.generation
       | T1 | T2 | T3 | T4 | T5 | T6 | T7 | T8 | T9 | T10 | T11 | T12 | T13 | T14
       | T15 ->
           assert false
@@ -440,10 +440,15 @@ struct
     in
     let* control =
       let open Payload in
-      let status = From_v3_no_gc_yet in
+      let status = No_gc_yet in
       let pl =
         let z = Int63.zero in
-        { dict_end_poff = z; suffix_end_poff = z; status }
+        {
+          dict_end_poff = z;
+          suffix_end_poff = z;
+          status;
+          upgraded_from_v3_to_v4 = false;
+        }
       in
       create_control_file ~overwrite config pl
     in
@@ -468,11 +473,11 @@ struct
     let* dead_header_size =
       match pl.status with
       | From_v1_v2_post_upgrade _ -> Ok legacy_io_header_size
-      | From_v3_gced _ ->
+      | Gced _ ->
           let indexing_strategy = Conf.indexing_strategy config in
           if Irmin_pack.Indexing_strategy.is_minimal indexing_strategy then Ok 0
           else Error `Only_minimal_indexing_strategy_allowed
-      | From_v3_no_gc_yet | From_v3_used_non_minimal_indexing_strategy -> Ok 0
+      | No_gc_yet | Used_non_minimal_indexing_strategy -> Ok 0
       | T1 | T2 | T3 | T4 | T5 | T6 | T7 | T8 | T9 | T10 | T11 | T12 | T13 | T14
       | T15 ->
           Error `V3_store_from_the_future
@@ -527,7 +532,14 @@ struct
         From_v1_v2_post_upgrade
           { entry_offset_at_upgrade_to_v3 = suffix_end_poff }
       in
-      let pl = { dict_end_poff; suffix_end_poff; status } in
+      let pl =
+        {
+          dict_end_poff;
+          suffix_end_poff;
+          status;
+          upgraded_from_v3_to_v4 = false;
+        }
+      in
       create_control_file ~overwrite:false config pl
     in
     let* () = Control.close control in
@@ -580,9 +592,7 @@ struct
     let* dead_header_size =
       match pl.status with
       | From_v1_v2_post_upgrade _ -> Ok legacy_io_header_size
-      | From_v3_no_gc_yet | From_v3_gced _
-      | From_v3_used_non_minimal_indexing_strategy ->
-          Ok 0
+      | No_gc_yet | Gced _ | Used_non_minimal_indexing_strategy -> Ok 0
       | T1 | T2 | T3 | T4 | T5 | T6 | T7 | T8 | T9 | T10 | T11 | T12 | T13 | T14
       | T15 ->
           Error `V3_store_from_the_future
@@ -653,7 +663,8 @@ struct
             | `Unknown_major_pack_version _ ) as e ->
             e)
 
-  let swap t ~generation ~new_suffix_start_offset ~new_suffix_end_offset =
+  let swap t ~generation ~new_suffix_start_offset ~new_suffix_end_offset
+      ~oldest_live_commit_offset =
     let open Result_syntax in
     [%log.debug
       "Gc in main: swap %d %#d %#d" generation
@@ -681,13 +692,14 @@ struct
         let status =
           match pl.status with
           | From_v1_v2_post_upgrade _ -> assert false
-          | From_v3_used_non_minimal_indexing_strategy -> assert false
+          | Used_non_minimal_indexing_strategy -> assert false
           | T1 | T2 | T3 | T4 | T5 | T6 | T7 | T8 | T9 | T10 | T11 | T12 | T13
           | T14 | T15 ->
               assert false
-          | From_v3_gced _ | From_v3_no_gc_yet ->
+          | Gced _ | No_gc_yet ->
               let suffix_start_offset = new_suffix_start_offset in
-              From_v3_gced { suffix_start_offset; generation }
+              Gced
+                { suffix_start_offset; generation; oldest_live_commit_offset }
         in
         { pl with status; suffix_end_poff }
       in
@@ -705,10 +717,9 @@ struct
   let generation t =
     let pl = Control.payload t.control in
     match pl.status with
-    | From_v1_v2_post_upgrade _ | From_v3_used_non_minimal_indexing_strategy ->
-        0
-    | From_v3_no_gc_yet -> 0
-    | From_v3_gced x -> x.generation
+    | From_v1_v2_post_upgrade _ | Used_non_minimal_indexing_strategy -> 0
+    | No_gc_yet -> 0
+    | Gced x -> x.generation
     | T1 | T2 | T3 | T4 | T5 | T6 | T7 | T8 | T9 | T10 | T11 | T12 | T13 | T14
     | T15 ->
         (* Unreachable *)
@@ -717,9 +728,8 @@ struct
   let gc_allowed t =
     let pl = Control.payload t.control in
     match pl.status with
-    | From_v1_v2_post_upgrade _ | From_v3_used_non_minimal_indexing_strategy ->
-        false
-    | From_v3_no_gc_yet | From_v3_gced _ -> true
+    | From_v1_v2_post_upgrade _ | Used_non_minimal_indexing_strategy -> false
+    | No_gc_yet | Gced _ -> true
     | T1 | T2 | T3 | T4 | T5 | T6 | T7 | T8 | T9 | T10 | T11 | T12 | T13 | T14
     | T15 ->
         (* Unreachable *)
diff --git a/src/irmin-pack/unix/file_manager_intf.ml b/src/irmin-pack/unix/file_manager_intf.ml
index 070bb0a629d..cab9773ef6a 100644
--- a/src/irmin-pack/unix/file_manager_intf.ml
+++ b/src/irmin-pack/unix/file_manager_intf.ml
@@ -243,6 +243,7 @@ module type S = sig
     generation:int ->
     new_suffix_start_offset:int63 ->
     new_suffix_end_offset:int63 ->
+    oldest_live_commit_offset:int63 ->
     (unit, [> Errs.t ]) result
   (** Swaps to using files from the GC [generation]. The offsets
       [new_suffix_start_offset] and [new_suffix_end_offset] are used to properly
diff --git a/src/irmin-pack/unix/gc.ml b/src/irmin-pack/unix/gc.ml
index 7586b33d8a5..50e450a2316 100644
--- a/src/irmin-pack/unix/gc.ml
+++ b/src/irmin-pack/unix/gc.ml
@@ -39,10 +39,19 @@ module Make (Args : Gc_args.S) = struct
     commit : read Commit_store.t;
     mutable partial_stats : Gc_stats.Main.t;
     mutable resulting_stats : Stats.Latest_gc.stats option;
+    oldest_live_commit_offset : int63;
   }
 
-  let v ~root ~generation ~unlink ~offset ~dispatcher ~fm ~contents ~node
-      ~commit commit_key =
+  let v ~root ~generation ~unlink ~dispatcher ~fm ~contents ~node ~commit
+      commit_key =
+    let offset, oldest_live_commit_offset =
+      let state : _ Pack_key.state = Pack_key.inspect commit_key in
+      match state with
+      | Direct x ->
+          let len = x.length |> Int63.of_int in
+          (Int63.Syntax.(x.offset + len), x.offset)
+      | Indexed _ -> assert false
+    in
     let partial_stats =
       let commit_offset = offset in
       let before_suffix_start_offset =
@@ -83,6 +92,7 @@ module Make (Args : Gc_args.S) = struct
     let partial_stats =
       Gc_stats.Main.finish_current_step partial_stats "before finalise"
     in
+
     {
       root;
       generation;
@@ -98,6 +108,7 @@ module Make (Args : Gc_args.S) = struct
       commit;
       partial_stats;
       resulting_stats = None;
+      oldest_live_commit_offset;
     }
 
   let open_new_suffix ~end_poff { root; generation; _ } =
@@ -142,6 +153,7 @@ module Make (Args : Gc_args.S) = struct
     let* () =
       Fm.swap t.fm ~generation:t.generation ~new_suffix_start_offset
         ~new_suffix_end_offset
+        ~oldest_live_commit_offset:t.oldest_live_commit_offset
     in
 
     (* No need to purge dict here, as it is global to the store. *)
diff --git a/src/irmin-pack/unix/gc.mli b/src/irmin-pack/unix/gc.mli
index ca8ac3a5082..cd5836f6fe1 100644
--- a/src/irmin-pack/unix/gc.mli
+++ b/src/irmin-pack/unix/gc.mli
@@ -27,7 +27,6 @@ module Make (Args : Gc_args.S) : sig
     root:string ->
     generation:int ->
     unlink:bool ->
-    offset:int63 ->
     dispatcher:Args.Dispatcher.t ->
     fm:Args.Fm.t ->
     contents:read Args.Contents_store.t ->
diff --git a/src/irmin-pack/unix/s.ml b/src/irmin-pack/unix/s.ml
index 5f893011702..78fd68337b7 100644
--- a/src/irmin-pack/unix/s.ml
+++ b/src/irmin-pack/unix/s.ml
@@ -127,6 +127,10 @@ module type S = sig
 
     val is_allowed : repo -> bool
     (** [is_allowed repo] returns true if a gc can be run on the store. *)
+
+    val oldest_live_commit : repo -> commit_key option
+    (** [oldest_live_commit repo] returns the commit key on which the latest,
+        finished gc was called on. *)
   end
 
   val integrity_check_inodes :
diff --git a/src/irmin-pack/version.ml b/src/irmin-pack/version.ml
index fb296b93500..e355bc90da5 100644
--- a/src/irmin-pack/version.ml
+++ b/src/irmin-pack/version.ml
@@ -17,13 +17,22 @@
 (* For every new version, update the [version] type and [versions]
    headers. *)
 
-type t = [ `V1 | `V2 | `V3 ] [@@deriving irmin]
+type t = [ `V1 | `V2 | `V3 | `V4 ] [@@deriving irmin]
 
 let latest = `V3
-let enum = [ (`V1, "00000001"); (`V2, "00000002"); (`V3, "00000003") ]
-let pp = Fmt.of_to_string (function `V1 -> "v1" | `V2 -> "v2" | `V3 -> "v3")
+
+let enum =
+  [ (`V1, "00000001"); (`V2, "00000002"); (`V3, "00000003"); (`V4, "00000004") ]
+
+let pp =
+  Fmt.of_to_string (function
+    | `V1 -> "v1"
+    | `V2 -> "v2"
+    | `V3 -> "v3"
+    | `V4 -> "v4")
+
 let to_bin v = List.assoc v enum
-let to_int = function `V1 -> 1 | `V2 -> 2 | `V3 -> 3
+let to_int = function `V1 -> 1 | `V2 -> 2 | `V3 -> 3 | `V4 -> 4
 let compare a b = Int.compare (to_int a) (to_int b)
 let encode_bin t f = to_bin t |> f
 
@@ -34,6 +43,7 @@ let decode_bin s offref =
     | "00000001" -> `V1
     | "00000002" -> `V2
     | "00000003" -> `V3
+    | "00000004" -> `V4
     | _ -> failwith "Couldn't decode pack version"
   in
   offref := !offref + 8;
diff --git a/src/irmin-pack/version.mli b/src/irmin-pack/version.mli
index 5480eb7b281..0169db76e30 100644
--- a/src/irmin-pack/version.mli
+++ b/src/irmin-pack/version.mli
@@ -26,7 +26,7 @@
     file). The upgrade of a store to [`V3] was done silently when opening a
     store in rw mode. *)
 
-type t = [ `V1 | `V2 | `V3 ] [@@deriving irmin]
+type t = [ `V1 | `V2 | `V3 | `V4 ] [@@deriving irmin]
 (** The type for version numbers. *)
 
 val compare : t -> t -> int
diff --git a/src/irmin-tezos-utils/show.ml b/src/irmin-tezos-utils/show.ml
index aa977cd0d00..2678d150e6e 100644
--- a/src/irmin-tezos-utils/show.ml
+++ b/src/irmin-tezos-utils/show.ml
@@ -720,10 +720,10 @@ let main store_path info_last_path info_next_path index_path =
   let max_offset =
     (* TODO: Rename [pl.suffix_end_poff] to [suffix_length] *)
     match pl.status with
-    | From_v1_v2_post_upgrade _ | From_v3_no_gc_yet
-    | From_v3_used_non_minimal_indexing_strategy ->
+    | From_v1_v2_post_upgrade _ | No_gc_yet | Used_non_minimal_indexing_strategy
+      ->
         pl.suffix_end_poff
-    | From_v3_gced x -> Int63.add x.suffix_start_offset pl.suffix_end_poff
+    | Gced x -> Int63.add x.suffix_start_offset pl.suffix_end_poff
     | T1 | T2 | T3 | T4 | T5 | T6 | T7 | T8 | T9 | T10 | T11 | T12 | T13 | T14
     | T15 ->
         assert false
diff --git a/test/irmin-cli/test_command_line.t b/test/irmin-cli/test_command_line.t
index a65906508e9..14f316d0b52 100644
--- a/test/irmin-cli/test_command_line.t
+++ b/test/irmin-cli/test_command_line.t
@@ -6,11 +6,11 @@ Create default config file
 
 Set a/b/c => 123 in ./test
   $ irmin set a/b/c 123
-  irmin: [WARNING] Updating the control file from [From_v3] to [From_v3_used_non_minimal_indexing_strategy]. It won't be possible to GC this irmin-pack store anymore.
+  irmin: [WARNING] Updating the control file to [Used_non_minimal_indexing_strategy]. It won't be possible to GC this irmin-pack store anymore.
 
 Set foo => bar in ./test1
   $ irmin set --root ./test1 foo bar
-  irmin: [WARNING] Updating the control file from [From_v3] to [From_v3_used_non_minimal_indexing_strategy]. It won't be possible to GC this irmin-pack store anymore.
+  irmin: [WARNING] Updating the control file to [Used_non_minimal_indexing_strategy]. It won't be possible to GC this irmin-pack store anymore.
 
 Check for a/b/c in ./test
   $ irmin get --root ./test a/b/c
@@ -91,6 +91,6 @@ Check mismatched hash function
 
 Clone a local repo
   $ irmin clone --root ./cloned ./test
-  irmin: [WARNING] Updating the control file from [From_v3] to [From_v3_used_non_minimal_indexing_strategy]. It won't be possible to GC this irmin-pack store anymore.
+  irmin: [WARNING] Updating the control file to [Used_non_minimal_indexing_strategy]. It won't be possible to GC this irmin-pack store anymore.
   $ irmin get --root ./cloned a/b/c
   123
diff --git a/test/irmin-pack/data/version_3_minimal_gced/index/log b/test/irmin-pack/data/version_3_minimal_gced/index/log
new file mode 100644
index 00000000000..e16fefc09ae
Binary files /dev/null and b/test/irmin-pack/data/version_3_minimal_gced/index/log differ
diff --git a/test/irmin-pack/data/version_3_minimal_gced/store.1.mapping b/test/irmin-pack/data/version_3_minimal_gced/store.1.mapping
new file mode 100644
index 00000000000..3d997fc6f96
Binary files /dev/null and b/test/irmin-pack/data/version_3_minimal_gced/store.1.mapping differ
diff --git a/test/irmin-pack/data/version_3_minimal_gced/store.1.prefix b/test/irmin-pack/data/version_3_minimal_gced/store.1.prefix
new file mode 100644
index 00000000000..6bfd270c6e5
Binary files /dev/null and b/test/irmin-pack/data/version_3_minimal_gced/store.1.prefix differ
diff --git a/test/irmin-pack/data/version_3_minimal_gced/store.1.suffix b/test/irmin-pack/data/version_3_minimal_gced/store.1.suffix
new file mode 100644
index 00000000000..7fa4cb187a7
Binary files /dev/null and b/test/irmin-pack/data/version_3_minimal_gced/store.1.suffix differ
diff --git a/test/irmin-pack/data/version_3_minimal_gced/store.branches b/test/irmin-pack/data/version_3_minimal_gced/store.branches
new file mode 100644
index 00000000000..b35ec9eb860
Binary files /dev/null and b/test/irmin-pack/data/version_3_minimal_gced/store.branches differ
diff --git a/test/irmin-pack/data/version_3_minimal_gced/store.control b/test/irmin-pack/data/version_3_minimal_gced/store.control
new file mode 100644
index 00000000000..14b85bca92d
Binary files /dev/null and b/test/irmin-pack/data/version_3_minimal_gced/store.control differ
diff --git a/test/irmin-pack/data/version_3_minimal_gced/store.dict b/test/irmin-pack/data/version_3_minimal_gced/store.dict
new file mode 100644
index 00000000000..167a469b4f0
Binary files /dev/null and b/test/irmin-pack/data/version_3_minimal_gced/store.dict differ
diff --git a/test/irmin-pack/test_gc.ml b/test/irmin-pack/test_gc.ml
index 34122245086..c89f087f502 100644
--- a/test/irmin-pack/test_gc.ml
+++ b/test/irmin-pack/test_gc.ml
@@ -567,6 +567,33 @@ module Gc = struct
     let* () = check_1 t c1_again in
     S.Repo.close t.repo
 
+  (** Check [Gc.oldest_live_commit]. *)
+  let oldest_live_commit () =
+    let* t = init () in
+    let check_oldest_live_commit expected =
+      let got = S.Gc.oldest_live_commit t.repo in
+      match (got, expected) with
+      | None, None -> ()
+      | Some got, Some expected ->
+          Alcotest.check_repr S.commit_key_t "oldest_live_commit" got
+            (S.Commit.key expected)
+      | _ -> Alcotest.fail "Check of oldest_live_commit failed"
+    in
+
+    let* t, c1 = commit_1 t in
+    let* t = checkout_exn t c1 in
+    check_oldest_live_commit None;
+    let* t, c2 = commit_2 t in
+    let* () = start_gc t c2 in
+    let* () = finalise_gc t in
+    check_oldest_live_commit (Some c2);
+    let* t = checkout_exn t c2 in
+    let* t, c3 = commit_3 t in
+    let* () = start_gc t c3 in
+    let* () = finalise_gc t in
+    check_oldest_live_commit (Some c3);
+    S.Repo.close t.repo
+
   let tests =
     [
       tc "Test one gc" one_gc;
@@ -583,6 +610,7 @@ module Gc = struct
       tc "Test gc during batch" gc_during_batch;
       tc "Test add back gced commit" add_back_gced_commit;
       tc "Test gc on similar commits" gc_similar_commits;
+      tc "Test oldest live commit" oldest_live_commit;
     ]
 end
 
diff --git a/test/irmin-pack/test_pack_version_bump.ml b/test/irmin-pack/test_pack_version_bump.ml
index 66642889efc..17504529883 100644
--- a/test/irmin-pack/test_pack_version_bump.ml
+++ b/test/irmin-pack/test_pack_version_bump.ml
@@ -95,7 +95,7 @@ module Util = struct
 
   (** Get the version of the underlying file; file is assumed to exist; file is
       assumed to be an Irmin_pack.IO.Unix file *)
-  let io_get_version ~root : [ `V1 | `V2 | `V3 ] =
+  let io_get_version ~root : [ `V1 | `V2 | `V3 | `V4 ] =
     File_manager.version ~root |> Errs.raise_if_error
 
   let alco_check_version ~pos ~expected ~actual =
diff --git a/test/irmin-pack/test_upgrade.ml b/test/irmin-pack/test_upgrade.ml
index 07b11a98752..f7faf0d63d5 100644
--- a/test/irmin-pack/test_upgrade.ml
+++ b/test/irmin-pack/test_upgrade.ml
@@ -22,6 +22,10 @@ let archive_v2_minimal = "test" / "irmin-pack" / "data" / "version_2_minimal"
 let archive_v2_always = "test" / "irmin-pack" / "data" / "version_2_always"
 let archive_v3_minimal = "test" / "irmin-pack" / "data" / "version_3_minimal"
 let archive_v3_always = "test" / "irmin-pack" / "data" / "version_3_always"
+
+let archive_v3_minimal_gced =
+  "test" / "irmin-pack" / "data" / "version_3_minimal_gced"
+
 let root_local_build = "_build" / "test-upgrade"
 
 type pack_entry = {
@@ -86,7 +90,7 @@ let key_of_entry x =
 type start_mode = From_v2 | From_v3 | From_scratch [@@deriving irmin]
 
 type setup = {
-  indexing_strategy : [ `always | `minimal ];
+  indexing_strategy : [ `always | `minimal | `minimal_gc ];
   start_mode : start_mode;
   lru_size : int;
 }
@@ -121,7 +125,8 @@ module Model = struct
     Hashtbl.replace t.dict "step-n01" ()
 
   let preload_suffix t =
-    Hashtbl.replace t.suffix borphan.o ();
+    if t.setup.indexing_strategy <> `minimal_gc then
+      Hashtbl.replace t.suffix borphan.o ();
     Hashtbl.replace t.suffix b01.o ();
     Hashtbl.replace t.suffix n01.o ();
     Hashtbl.replace t.suffix n0.o ();
@@ -459,6 +464,8 @@ let create_test_env setup =
     | From_v3 ->
         let root_archive =
           if setup.indexing_strategy = `always then archive_v3_always
+          else if setup.indexing_strategy = `minimal_gc then
+            archive_v3_minimal_gced
           else archive_v3_minimal
         in
         setup_test_env ~root_archive ~root_local_build
@@ -523,7 +530,9 @@ let gc_rw t =
                   Store.gc repo)
             in
             raise Skip_the_rest_of_that_test
-        | (From_v3 | From_scratch), `minimal -> Store.gc repo
+        | (From_v3 | From_scratch), `minimal
+        | (From_v3 | From_scratch), `minimal_gc ->
+            Store.gc repo
       in
       Lwt.return_unit
 
@@ -667,6 +676,10 @@ let test start_mode indexing_strategy =
   let* () = test start_mode indexing_strategy 100 in
   Lwt.return_unit
 
+let test_gced_store () =
+  let* () = test From_v3 `minimal_gc in
+  Lwt.return_unit
+
 (** Product on indexing_strategy *)
 let test start_mode () =
   let* () = test start_mode `minimal in
@@ -682,4 +695,6 @@ let tests =
         test From_v2 ());
     Alcotest_lwt.test_case "upgrade From_scratch" `Quick (fun _switch () ->
         test From_scratch ());
+    Alcotest_lwt.test_case "upgrade From_v3 after Gc" `Quick (fun _switch () ->
+        test_gced_store ());
   ]