diff --git a/master_changes.md b/master_changes.md
index 9d195a39fc7..11542ad8b3c 100644
--- a/master_changes.md
+++ b/master_changes.md
@@ -72,6 +72,7 @@ users)
 ## External dependencies
 
 ## Format upgrade
+  * Fix switch and repo format upgrade on Windows. A block occurred because the global lock fd was reopened instead of using the one already opened.  [#6839 @rjbou]
 
 ## Sandbox
   * Allow the macOS sandbox to write in the `/var/folders/` and `/var/db/mds/` directories as it is required by some of macOS core tools [#4797 @kit-ty-kate - fix #4389 #6460]
@@ -164,6 +165,7 @@ users)
   * `OpamRepositoryState.load_opams_from_diff` track added packages to avoid removing version-equivalent packages [#6774 @arozovyk fix #6754]
   * `OpamGlobalState.all_installed_versions`: was added [#6818 @dra27]
   * `OpamGlobalState.installed_versions`: was removed [#6818 @dra27]
+  * `OpamStateTypes.global_state`: add field `lock` that contains the global lock (not config one) [#6839 @rjbou]
 
 ## opam-solver
 
diff --git a/src/client/opamAdminCommand.ml b/src/client/opamAdminCommand.ml
index 0b57ee84b33..60d27fa2797 100644
--- a/src/client/opamAdminCommand.ml
+++ b/src/client/opamAdminCommand.ml
@@ -1087,6 +1087,7 @@ let get_virtual_switch_state repo_root env =
   in
   let gt = {
     global_lock = OpamSystem.lock_none;
+    lock = OpamSystem.lock_none;
     root = OpamStateConfig.(!r.root_dir);
     config = OpamStd.Option.Op.(OpamStateConfig.(
         load ~lock_kind:`Lock_read !r.root_dir) +!
diff --git a/src/state/opamFormatUpgrade.ml b/src/state/opamFormatUpgrade.ml
index ba53e469357..2d3d40296fd 100644
--- a/src/state/opamFormatUpgrade.ml
+++ b/src/state/opamFormatUpgrade.ml
@@ -1204,12 +1204,8 @@ let flock_root =
     ) in
     fun () -> Lazy.force t
   in
-  fun ?global_lock kind root ->
+  fun ~global_lock kind ->
     try
-      let global_lock = match global_lock with
-        | Some g -> g
-        | None -> OpamFilename.flock `Lock_read (OpamPath.lock root)
-      in
       OpamFilename.with_flock_upgrade kind ?dontblock:(dontblock ()) global_lock
     with OpamSystem.Locked ->
       OpamConsole.error_and_exit `Locked
@@ -1345,7 +1341,7 @@ let as_necessary ?reinit requested_lock global_lock root config =
       (OpamFilename.Dir.to_string root)
       (OpamVersion.to_string root_version)
       (OpamVersion.to_string latest_version);
-  flock_root global_lock_kind ~global_lock root @@ fun _ ->
+  flock_root ~global_lock global_lock_kind @@ fun _ ->
   if not on_the_fly then
     if need_hard_upg then
       if is_dev &&
@@ -1416,7 +1412,7 @@ let as_necessary_repo_switch_t updates read_f lock_kind gt =
         (OpamVersion.to_string written_root_version)
         (OpamVersion.to_string (OpamFile.Config.opam_root_version config));
       if OpamConsole.confirm "Continue?" then
-        flock_root `Lock_write root @@ fun _ ->
+        flock_root `Lock_write ~global_lock:gt.lock @@ fun _ ->
         (* we keep only light upgrades as hard upgrade is already handled by
            global state loading, so we must not have to handle hard upgrades
            as this point. *)
diff --git a/src/state/opamGlobalState.ml b/src/state/opamGlobalState.ml
index cebe6980f60..211fd54f6e7 100644
--- a/src/state/opamGlobalState.ml
+++ b/src/state/opamGlobalState.ml
@@ -139,12 +139,14 @@ let load lock_kind =
           acc)
       global_variables eval_variables
   in
-  { global_lock = config_lock;
+  {
+    lock = global_lock;
+    global_lock = config_lock;
     root;
     config;
     global_variables;
     global_state_to_upgrade;
-    }
+  }
 
 let switches gt =
   OpamFile.Config.installed_switches gt.config
diff --git a/src/state/opamStateTypes.mli b/src/state/opamStateTypes.mli
index 2cee9a48630..ad9fc7d50c9 100644
--- a/src/state/opamStateTypes.mli
+++ b/src/state/opamStateTypes.mli
@@ -51,6 +51,10 @@ type gt_changes = { gtc_repo: bool; gtc_switch: bool }
 (** Global state corresponding to an opam root and its configuration *)
 type +'lock global_state = {
   global_lock: OpamSystem.lock;
+  (** Global config lock file *)
+
+  lock: OpamSystem.lock;
+  (** Global lock file *)
 
   root: OpamPath.t;
   (** The global opam root path (caution: this is stored here but some code may