diff --git a/contrib/scalar/scalar.c b/contrib/scalar/scalar.c
index 6bebba0b51f..234a7dce479 100644
--- a/contrib/scalar/scalar.c
+++ b/contrib/scalar/scalar.c
@@ -487,22 +487,77 @@ static int cmd_register(int argc, const char **argv)
 	return register_dir();
 }
 
+static int get_scalar_repos(const char *key, const char *value, void *data)
+{
+	struct string_list *list = data;
+
+	if (!strcmp(key, "scalar.repo"))
+		string_list_append(list, value);
+
+	return 0;
+}
+
 static int cmd_reconfigure(int argc, const char **argv)
 {
+	int all = 0;
 	struct option options[] = {
+		OPT_BOOL('a', "all", &all,
+			 N_("reconfigure all registered enlistments")),
 		OPT_END(),
 	};
 	const char * const usage[] = {
-		N_("scalar reconfigure [<enlistment>]"),
+		N_("scalar reconfigure [--all | <enlistment>]"),
 		NULL
 	};
+	struct string_list scalar_repos = STRING_LIST_INIT_DUP;
+	int i, res = 0;
+	struct repository r = { NULL };
+	struct strbuf commondir = STRBUF_INIT, gitdir = STRBUF_INIT;
 
 	argc = parse_options(argc, argv, NULL, options,
 			     usage, 0);
 
-	setup_enlistment_directory(argc, argv, usage, options, NULL);
+	if (!all) {
+		setup_enlistment_directory(argc, argv, usage, options, NULL);
+
+		return set_recommended_config(1);
+	}
+
+	if (argc > 0)
+		usage_msg_opt(_("--all or <enlistment>, but not both"),
+			      usage, options);
+
+	git_config(get_scalar_repos, &scalar_repos);
 
-	return set_recommended_config(1);
+	for (i = 0; i < scalar_repos.nr; i++) {
+		const char *dir = scalar_repos.items[i].string;
+
+		strbuf_reset(&commondir);
+		strbuf_reset(&gitdir);
+
+		if (chdir(dir) < 0) {
+			warning_errno(_("could not switch to '%s'"), dir);
+			res = -1;
+		} else if (discover_git_directory(&commondir, &gitdir) < 0) {
+			warning_errno(_("git repository gone in '%s'"), dir);
+			res = -1;
+		} else {
+			git_config_clear();
+
+			the_repository = &r;
+			r.commondir = commondir.buf;
+			r.gitdir = gitdir.buf;
+
+			if (set_recommended_config(1) < 0)
+				res = -1;
+		}
+	}
+
+	string_list_clear(&scalar_repos, 1);
+	strbuf_release(&commondir);
+	strbuf_release(&gitdir);
+
+	return res;
 }
 
 static int cmd_run(int argc, const char **argv)
diff --git a/contrib/scalar/scalar.txt b/contrib/scalar/scalar.txt
index 89fd7901585..737cf563c1a 100644
--- a/contrib/scalar/scalar.txt
+++ b/contrib/scalar/scalar.txt
@@ -13,7 +13,7 @@ scalar list
 scalar register [<enlistment>]
 scalar unregister [<enlistment>]
 scalar run ( all | config | commit-graph | fetch | loose-objects | pack-files ) [<enlistment>]
-scalar reconfigure <enlistment>
+scalar reconfigure [ --all | <enlistment> ]
 
 DESCRIPTION
 -----------
@@ -32,8 +32,8 @@ an existing Git worktree with Scalar whose name is not `src`, the enlistment
 will be identical to the worktree.
 
 The `scalar` command implements various subcommands, and different options
-depending on the subcommand. With the exception of `clone` and `list`, all
-subcommands expect to be run in an enlistment.
+depending on the subcommand. With the exception of `clone`, `list` and
+`reconfigure --all`, all subcommands expect to be run in an enlistment.
 
 COMMANDS
 --------
@@ -125,6 +125,9 @@ After a Scalar upgrade, or when the configuration of a Scalar enlistment
 was somehow corrupted or changed by mistake, this subcommand allows to
 reconfigure the enlistment.
 
+With the `--all` option, all enlistments currently registered with Scalar
+will be reconfigured. Use this option after each Scalar upgrade.
+
 SEE ALSO
 --------
 linkgit:git-clone[1], linkgit:git-maintenance[1].
diff --git a/contrib/scalar/t/t9099-scalar.sh b/contrib/scalar/t/t9099-scalar.sh
index e6d74a06ca0..5fe7fabd0e5 100755
--- a/contrib/scalar/t/t9099-scalar.sh
+++ b/contrib/scalar/t/t9099-scalar.sh
@@ -70,6 +70,9 @@ test_expect_success 'scalar reconfigure' '
 	scalar register one &&
 	git -C one/src config core.preloadIndex false &&
 	scalar reconfigure one &&
+	test true = "$(git -C one/src config core.preloadIndex)" &&
+	git -C one/src config core.preloadIndex false &&
+	scalar reconfigure -a &&
 	test true = "$(git -C one/src config core.preloadIndex)"
 '
 
