diff --git a/TODO b/TODO
index 2cb1f6848b..d80ca4d717 100644
--- a/TODO
+++ b/TODO
@@ -134,11 +134,6 @@ Features:
 * in pid1: include ExecStart= cmdlines (and other Exec*= cmdlines) in polkit
   request, so that policies can match against command lines.
 
-* in pid1: before processing subscribed_as_strv when we come back from a
-  bus disconnect, let's check the bus 128bit id reported by the bus driver: if
-  it doesn't equal the one from before we should skip reinstalling the bus
-  tracker objects.
-
 * account number of units currently in activating/active/deactivating state in
   each slice, and expose this as a property of the slice, given this is a key
   metric of the resource management entity that a slice is. (maybe add a 2nd
diff --git a/src/core/dbus-cgroup.c b/src/core/dbus-cgroup.c
index fd48f3b07c..c99f1e29ac 100644
--- a/src/core/dbus-cgroup.c
+++ b/src/core/dbus-cgroup.c
@@ -7,6 +7,7 @@
 #include "bpf-firewall.h"
 #include "bpf-foreign.h"
 #include "bus-get-properties.h"
+#include "bus-message-util.h"
 #include "bus-util.h"
 #include "cgroup-util.h"
 #include "cgroup.h"
diff --git a/src/core/dbus-manager.c b/src/core/dbus-manager.c
index 99e3ea12ac..4b61002eac 100644
--- a/src/core/dbus-manager.c
+++ b/src/core/dbus-manager.c
@@ -12,6 +12,7 @@
 #include "bus-common-errors.h"
 #include "bus-get-properties.h"
 #include "bus-log-control-api.h"
+#include "bus-message-util.h"
 #include "bus-util.h"
 #include "chase.h"
 #include "confidential-virt.h"
diff --git a/src/core/dbus.c b/src/core/dbus.c
index 58cd1ee175..a2a2611a03 100644
--- a/src/core/dbus.c
+++ b/src/core/dbus.c
@@ -5,6 +5,7 @@
 #include <unistd.h>
 
 #include "sd-bus.h"
+#include "sd-id128.h"
 
 #include "alloc-util.h"
 #include "bus-common-errors.h"
@@ -774,6 +775,24 @@ static int bus_on_connection(sd_event_source *s, int fd, uint32_t revents, void
         return 0;
 }
 
+static int bus_track_coldplug(sd_bus *bus, sd_bus_track **t, char * const *l) {
+        int r;
+
+        assert(bus);
+        assert(t);
+
+        if (strv_isempty(l))
+                return 0;
+
+        if (!*t) {
+                r = sd_bus_track_new(bus, t, NULL, NULL);
+                if (r < 0)
+                        return r;
+        }
+
+        return bus_track_add_name_many(*t, l);
+}
+
 static int bus_setup_api(Manager *m, sd_bus *bus) {
         char *name;
         Unit *u;
@@ -860,10 +879,15 @@ int bus_init_api(Manager *m) {
         if (r < 0)
                 return log_error_errno(r, "Failed to set up API bus: %m");
 
-        (void) bus_track_coldplug(bus, &m->subscribed, /* recursive= */ false, m->subscribed_as_strv);
+        r = bus_get_instance_id(bus, &m->bus_id);
+        if (r < 0)
+                log_warning_errno(r, "Failed to query API bus instance ID, not deserializing subscriptions: %m");
+        else if (sd_id128_is_null(m->deserialized_bus_id) || sd_id128_equal(m->bus_id, m->deserialized_bus_id))
+                (void) bus_track_coldplug(bus, &m->subscribed, m->subscribed_as_strv);
         m->subscribed_as_strv = strv_free(m->subscribed_as_strv);
-        m->api_bus = TAKE_PTR(bus);
+        m->deserialized_bus_id = SD_ID128_NULL;
 
+        m->api_bus = TAKE_PTR(bus);
         return 0;
 }
 
@@ -1015,6 +1039,9 @@ static void destroy_bus(Manager *m, sd_bus **bus) {
                         log_warning_errno(r, "Failed to serialize api subscribers, ignoring: %m");
                 strv_free_and_replace(m->subscribed_as_strv, subscribed);
 
+                m->deserialized_bus_id = m->bus_id;
+                m->bus_id = SD_ID128_NULL;
+
                 m->subscribed = sd_bus_track_unref(m->subscribed);
         }
 
@@ -1163,30 +1190,6 @@ void bus_track_serialize(sd_bus_track *t, FILE *f, const char *prefix) {
         }
 }
 
-int bus_track_coldplug(sd_bus *bus, sd_bus_track **t, bool recursive, char **l) {
-        int r;
-
-        assert(t);
-
-        if (strv_isempty(l))
-                return 0;
-
-        if (!bus)
-                return 0;
-
-        if (!*t) {
-                r = sd_bus_track_new(bus, t, NULL, NULL);
-                if (r < 0)
-                        return r;
-        }
-
-        r = sd_bus_track_set_recursive(*t, recursive);
-        if (r < 0)
-                return r;
-
-        return bus_track_add_name_many(*t, l);
-}
-
 uint64_t manager_bus_n_queued_write(Manager *m) {
         uint64_t c = 0;
         sd_bus *b;
diff --git a/src/core/dbus.h b/src/core/dbus.h
index eb1baf6049..0f81102fc1 100644
--- a/src/core/dbus.h
+++ b/src/core/dbus.h
@@ -19,7 +19,6 @@ void bus_done(Manager *m);
 int bus_fdset_add_all(Manager *m, FDSet *fds);
 
 void bus_track_serialize(sd_bus_track *t, FILE *f, const char *prefix);
-int bus_track_coldplug(sd_bus *bus, sd_bus_track **t, bool recursive, char **l);
 
 int bus_foreach_bus(Manager *m, sd_bus_track *subscribed2, int (*send_message)(sd_bus *bus, void *userdata), void *userdata);
 
diff --git a/src/core/manager-serialize.c b/src/core/manager-serialize.c
index 4aecb6de2f..fbc1475bcf 100644
--- a/src/core/manager-serialize.c
+++ b/src/core/manager-serialize.c
@@ -158,6 +158,7 @@ int manager_serialize(
         (void) serialize_ratelimit(f, "dump-ratelimit", &m->dump_ratelimit);
         (void) serialize_ratelimit(f, "reload-reexec-ratelimit", &m->reload_reexec_ratelimit);
 
+        (void) serialize_id128(f, "bus-id", m->bus_id);
         bus_track_serialize(m->subscribed, f, "subscribed");
 
         r = dynamic_user_serialize(m, f, fds);
@@ -487,7 +488,12 @@ int manager_deserialize(Manager *m, FILE *f, FDSet *fds) {
                         manager_deserialize_gid_refs_one(m, val);
                 else if ((val = startswith(l, "exec-runtime=")))
                         (void) exec_shared_runtime_deserialize_one(m, val, fds);
-                else if ((val = startswith(l, "subscribed="))) {
+                else if ((val = startswith(l, "bus-id="))) {
+
+                        r = sd_id128_from_string(val, &m->deserialized_bus_id);
+                        if (r < 0)
+                                return r;
+                } else if ((val = startswith(l, "subscribed="))) {
 
                         r = strv_extend(&m->subscribed_as_strv, val);
                         if (r < 0)
diff --git a/src/core/manager.c b/src/core/manager.c
index c4c1b9022c..8f1dc626c2 100644
--- a/src/core/manager.c
+++ b/src/core/manager.c
@@ -1817,15 +1817,16 @@ Manager* manager_free(Manager *m) {
         hashmap_free(m->uid_refs);
         hashmap_free(m->gid_refs);
 
-        for (ExecDirectoryType dt = 0; dt < _EXEC_DIRECTORY_TYPE_MAX; dt++)
-                m->prefix[dt] = mfree(m->prefix[dt]);
+        FOREACH_ARRAY(i, m->prefix, _EXEC_DIRECTORY_TYPE_MAX)
+                free(*i);
+
         free(m->received_credentials_directory);
         free(m->received_encrypted_credentials_directory);
 
         free(m->watchdog_pretimeout_governor);
         free(m->watchdog_pretimeout_governor_overridden);
 
-        m->fw_ctx = fw_ctx_free(m->fw_ctx);
+        fw_ctx_free(m->fw_ctx);
 
 #if BPF_FRAMEWORK
         bpf_restrict_fs_destroy(m->restrict_fs);
@@ -2142,12 +2143,6 @@ int manager_startup(Manager *m, FILE *serialization, FDSet *fds, const char *roo
                 /* Connect to the bus if we are good for it */
                 manager_setup_bus(m);
 
-                /* Now that we are connected to all possible buses, let's deserialize who is tracking us. */
-                r = bus_track_coldplug(m->api_bus, &m->subscribed, false, m->subscribed_as_strv);
-                if (r < 0)
-                        log_warning_errno(r, "Failed to deserialized tracked clients, ignoring: %m");
-                m->subscribed_as_strv = strv_free(m->subscribed_as_strv);
-
                 r = manager_varlink_init(m);
                 if (r < 0)
                         log_warning_errno(r, "Failed to set up Varlink, ignoring: %m");
@@ -3806,6 +3801,11 @@ int manager_reload(Manager *m) {
         (void) manager_setup_handoff_timestamp_fd(m);
         (void) manager_setup_pidref_transport_fd(m);
 
+        /* Clean up deserialized bus track information. They're never consumed during reload (as opposed to
+         * reexec) since we do not disconnect from the bus. */
+        m->subscribed_as_strv = strv_free(m->subscribed_as_strv);
+        m->deserialized_bus_id = SD_ID128_NULL;
+
         /* Third, fire things up! */
         manager_coldplug(m);
 
diff --git a/src/core/manager.h b/src/core/manager.h
index 7016eab2d3..c5bd242968 100644
--- a/src/core/manager.h
+++ b/src/core/manager.h
@@ -335,13 +335,16 @@ struct Manager {
         int private_listen_fd;
         sd_event_source *private_listen_event_source;
 
-        /* Contains all the clients that are subscribed to signals via
-        the API bus. Note that private bus connections are always
-        considered subscribes, since they last for very short only,
-        and it is much simpler that way. */
+        /* Contains all the clients that are subscribed to signals via the API bus. Note that private bus
+         * connections are always considered subscribes, since they last for very short only, and it is
+         * much simpler that way. */
         sd_bus_track *subscribed;
         char **subscribed_as_strv;
 
+        /* The bus id of API bus acquired through org.freedesktop.DBus.GetId, which before deserializing
+         * subscriptions we'd use to verify the bus is still the same instance as before. */
+        sd_id128_t bus_id, deserialized_bus_id;
+
         /* This is used during reloading: before the reload we queue
          * the reply message here, and afterwards we send it */
         sd_bus_message *pending_reload_message;
diff --git a/src/core/unit-serialize.c b/src/core/unit-serialize.c
index 82789fdbf4..78ceb006a4 100644
--- a/src/core/unit-serialize.c
+++ b/src/core/unit-serialize.c
@@ -117,8 +117,7 @@ int unit_serialize_state(Unit *u, FILE *f, FDSet *fds, bool switching_root) {
         if (gid_is_valid(u->ref_gid))
                 (void) serialize_item_format(f, "ref-gid", GID_FMT, u->ref_gid);
 
-        if (!sd_id128_is_null(u->invocation_id))
-                (void) serialize_item_format(f, "invocation-id", SD_ID128_FORMAT_STR, SD_ID128_FORMAT_VAL(u->invocation_id));
+        (void) serialize_id128(f, "invocation-id", u->invocation_id);
 
         (void) serialize_item(f, "freezer-state", freezer_state_to_string(u->freezer_state));
 
diff --git a/src/home/homed-manager-bus.c b/src/home/homed-manager-bus.c
index 69c7680b9e..08c917aee2 100644
--- a/src/home/homed-manager-bus.c
+++ b/src/home/homed-manager-bus.c
@@ -4,6 +4,7 @@
 
 #include "alloc-util.h"
 #include "bus-common-errors.h"
+#include "bus-message-util.h"
 #include "bus-polkit.h"
 #include "format-util.h"
 #include "home-util.h"
@@ -704,17 +705,17 @@ static int method_rebalance(sd_bus_message *message, void *userdata, sd_bus_erro
         int r;
 
         r = manager_schedule_rebalance(m, /* immediately= */ true);
-        if (r == 0)
-                return sd_bus_reply_method_errorf(message, BUS_ERROR_REBALANCE_NOT_NEEDED, "No home directories need rebalancing.");
         if (r < 0)
                 return r;
+        if (r == 0)
+                return sd_bus_reply_method_errorf(message, BUS_ERROR_REBALANCE_NOT_NEEDED, "No home directories need rebalancing.");
 
         /* Keep a reference to this message, so that we can reply to it once we are done */
-        r = set_ensure_put(&m->rebalance_queued_method_calls, &bus_message_hash_ops, message);
+        r = set_ensure_consume(&m->rebalance_queued_method_calls, &bus_message_hash_ops, sd_bus_message_ref(message));
         if (r < 0)
                 return log_error_errno(r, "Failed to track rebalance bus message: %m");
+        assert(r > 0);
 
-        sd_bus_message_ref(message);
         return 1;
 }
 
diff --git a/src/hostname/hostnamectl.c b/src/hostname/hostnamectl.c
index cd4f86af80..2d1334f654 100644
--- a/src/hostname/hostnamectl.c
+++ b/src/hostname/hostnamectl.c
@@ -18,6 +18,7 @@
 #include "bus-error.h"
 #include "bus-locator.h"
 #include "bus-map-properties.h"
+#include "bus-message-util.h"
 #include "format-table.h"
 #include "hostname-setup.h"
 #include "hostname-util.h"
diff --git a/src/login/logind-brightness.c b/src/login/logind-brightness.c
index 40bcb39ce0..b3e7718394 100644
--- a/src/login/logind-brightness.c
+++ b/src/login/logind-brightness.c
@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
+#include "bus-message-util.h"
 #include "bus-util.h"
 #include "device-util.h"
 #include "hash-funcs.h"
@@ -173,10 +174,9 @@ static int set_add_message(Set **set, sd_bus_message *message) {
         if (r <= 0)
                 return r;
 
-        r = set_ensure_put(set, &bus_message_hash_ops, message);
+        r = set_ensure_consume(set, &bus_message_hash_ops, sd_bus_message_ref(message));
         if (r <= 0)
                 return r;
-        sd_bus_message_ref(message);
 
         return 1;
 }
diff --git a/src/machine/machinectl.c b/src/machine/machinectl.c
index 39d3f3aed8..91bef1a5e9 100644
--- a/src/machine/machinectl.c
+++ b/src/machine/machinectl.c
@@ -21,6 +21,7 @@
 #include "bus-error.h"
 #include "bus-locator.h"
 #include "bus-map-properties.h"
+#include "bus-message-util.h"
 #include "bus-print-properties.h"
 #include "bus-unit-procs.h"
 #include "bus-unit-util.h"
diff --git a/src/machine/machined-dbus.c b/src/machine/machined-dbus.c
index fc50d3f147..e50ed7e0df 100644
--- a/src/machine/machined-dbus.c
+++ b/src/machine/machined-dbus.c
@@ -10,6 +10,7 @@
 #include "bus-common-errors.h"
 #include "bus-get-properties.h"
 #include "bus-locator.h"
+#include "bus-message-util.h"
 #include "bus-polkit.h"
 #include "cgroup-util.h"
 #include "discover-image.h"
diff --git a/src/run/run.c b/src/run/run.c
index 28953a6514..4a7a5d939c 100644
--- a/src/run/run.c
+++ b/src/run/run.c
@@ -15,6 +15,7 @@
 #include "bus-error.h"
 #include "bus-locator.h"
 #include "bus-map-properties.h"
+#include "bus-message-util.h"
 #include "bus-unit-util.h"
 #include "bus-wait-for-jobs.h"
 #include "calendarspec.h"
diff --git a/src/shared/bus-get-properties.c b/src/shared/bus-get-properties.c
index 53e5d6b99f..bf267a23a5 100644
--- a/src/shared/bus-get-properties.c
+++ b/src/shared/bus-get-properties.c
@@ -1,6 +1,7 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
 #include "bus-get-properties.h"
+#include "bus-message-util.h"
 #include "rlimit-util.h"
 #include "stdio-util.h"
 #include "string-util.h"
@@ -164,3 +165,21 @@ int bus_property_get_rlimit(
 
         return sd_bus_message_append(reply, "t", u);
 }
+
+int bus_property_get_string_set(
+                sd_bus *bus,
+                const char *path,
+                const char *interface,
+                const char *property,
+                sd_bus_message *reply,
+                void *userdata,
+                sd_bus_error *error) {
+
+        Set **s = ASSERT_PTR(userdata);
+
+        assert(bus);
+        assert(property);
+        assert(reply);
+
+        return bus_message_append_string_set(reply, *s);
+}
diff --git a/src/shared/bus-get-properties.h b/src/shared/bus-get-properties.h
index 4c35126502..9ddf5454de 100644
--- a/src/shared/bus-get-properties.h
+++ b/src/shared/bus-get-properties.h
@@ -52,6 +52,8 @@ assert_cc(sizeof(mode_t) == sizeof(uint32_t));
 
 int bus_property_get_rlimit(sd_bus *bus, const char *path, const char *interface, const char *property, sd_bus_message *reply, void *userdata, sd_bus_error *error);
 
+int bus_property_get_string_set(sd_bus *bus, const char *path, const char *interface, const char *property, sd_bus_message *reply, void *userdata, sd_bus_error *error);
+
 #define BUS_DEFINE_PROPERTY_GET_GLOBAL(function, bus_type, val)         \
         int function(sd_bus *bus,                                       \
                      const char *path,                                  \
diff --git a/src/shared/bus-map-properties.c b/src/shared/bus-map-properties.c
index a6cd752894..18d83c336f 100644
--- a/src/shared/bus-map-properties.c
+++ b/src/shared/bus-map-properties.c
@@ -5,6 +5,7 @@
 #include "bus-util.h"
 #include "strv.h"
 #include "bus-message.h"
+#include "bus-message-util.h"
 
 int bus_map_id128(sd_bus *bus, const char *member, sd_bus_message *m, sd_bus_error *error, void *userdata) {
         sd_id128_t *p = userdata;
diff --git a/src/shared/bus-message-util.c b/src/shared/bus-message-util.c
index d8c483ef62..8da112cacc 100644
--- a/src/shared/bus-message-util.c
+++ b/src/shared/bus-message-util.c
@@ -7,6 +7,35 @@
 #include "copy.h"
 #include "resolve-util.h"
 
+int bus_message_read_id128(sd_bus_message *m, sd_id128_t *ret) {
+        const void *a;
+        size_t sz;
+        int r;
+
+        assert(m);
+
+        r = sd_bus_message_read_array(m, 'y', &a, &sz);
+        if (r < 0)
+                return r;
+
+        switch (sz) {
+
+        case 0:
+                if (ret)
+                        *ret = SD_ID128_NULL;
+                return 0;
+
+        case sizeof(sd_id128_t):
+                if (ret)
+                        memcpy(ret, a, sz);
+                return !memeqzero(a, sz); /* This mimics sd_id128_is_null(), but ret may be NULL,
+                                           * and a may be misaligned, so use memeqzero() here. */
+
+        default:
+                return -EINVAL;
+        }
+}
+
 int bus_message_read_ifindex(sd_bus_message *message, sd_bus_error *error, int *ret) {
         int ifindex, r;
 
@@ -187,6 +216,25 @@ clear:
         return r;
 }
 
+int bus_message_append_string_set(sd_bus_message *m, const Set *set) {
+        int r;
+
+        assert(m);
+
+        r = sd_bus_message_open_container(m, 'a', "s");
+        if (r < 0)
+                return r;
+
+        const char *s;
+        SET_FOREACH(s, set) {
+                r = sd_bus_message_append(m, "s", s);
+                if (r < 0)
+                        return r;
+        }
+
+        return sd_bus_message_close_container(m);
+}
+
 int bus_message_dump_string(sd_bus_message *message) {
         const char *s;
         int r;
@@ -217,3 +265,7 @@ int bus_message_dump_fd(sd_bus_message *message) {
 
         return 0;
 }
+
+DEFINE_HASH_OPS_WITH_VALUE_DESTRUCTOR(bus_message_hash_ops,
+                                      void, trivial_hash_func, trivial_compare_func,
+                                      sd_bus_message, sd_bus_message_unref);
diff --git a/src/shared/bus-message-util.h b/src/shared/bus-message-util.h
index 50025766c2..d4a05f5b9c 100644
--- a/src/shared/bus-message-util.h
+++ b/src/shared/bus-message-util.h
@@ -6,6 +6,8 @@
 #include "in-addr-util.h"
 #include "socket-netlink.h"
 
+int bus_message_read_id128(sd_bus_message *m, sd_id128_t *ret);
+
 int bus_message_read_ifindex(sd_bus_message *message, sd_bus_error *error, int *ret);
 int bus_message_read_family(sd_bus_message *message, sd_bus_error *error, int *ret);
 int bus_message_read_in_addr_auto(sd_bus_message *message, sd_bus_error *error, int *ret_family, union in_addr_union *ret_addr);
@@ -17,5 +19,9 @@ int bus_message_read_dns_servers(
                         struct in_addr_full ***ret_dns,
                         size_t *ret_n_dns);
 
+int bus_message_append_string_set(sd_bus_message *m, const Set *s);
+
 int bus_message_dump_string(sd_bus_message *message);
 int bus_message_dump_fd(sd_bus_message *message);
+
+extern const struct hash_ops bus_message_hash_ops;
diff --git a/src/shared/bus-util.c b/src/shared/bus-util.c
index e38433ddc0..05926771d2 100644
--- a/src/shared/bus-util.c
+++ b/src/shared/bus-util.c
@@ -686,7 +686,7 @@ int bus_path_decode_unique(const char *path, const char *prefix, char **ret_send
         return 1;
 }
 
-int bus_track_add_name_many(sd_bus_track *t, char **l) {
+int bus_track_add_name_many(sd_bus_track *t, char * const *l) {
         int r = 0;
 
         assert(t);
@@ -700,16 +700,15 @@ int bus_track_add_name_many(sd_bus_track *t, char **l) {
 
 int bus_track_to_strv(sd_bus_track *t, char ***ret) {
         _cleanup_strv_free_ char **subscribed = NULL;
-        int r = 0;
+        int r;
 
         assert(ret);
 
         for (const char *n = sd_bus_track_first(t); n; n = sd_bus_track_next(t)) {
-                r = sd_bus_track_count_name(t, n);
-                if (r < 0)
-                        return r;
+                int c = sd_bus_track_count_name(t, n);
+                assert(c >= 0);
 
-                for (int j = 0; j < r; j++) {
+                for (int j = 0; j < c; j++) {
                         r = strv_extend(&subscribed, n);
                         if (r < 0)
                                 return r;
@@ -717,7 +716,7 @@ int bus_track_to_strv(sd_bus_track *t, char ***ret) {
         }
 
         *ret = TAKE_PTR(subscribed);
-        return r;
+        return 0;
 }
 
 int bus_open_system_watch_bind_with_description(sd_bus **ret, const char *description) {
@@ -862,53 +861,6 @@ int bus_register_malloc_status(sd_bus *bus, const char *destination) {
         return 0;
 }
 
-static void bus_message_unref_wrapper(void *m) {
-        sd_bus_message_unref(m);
-}
-
-const struct hash_ops bus_message_hash_ops = {
-        .hash = trivial_hash_func,
-        .compare = trivial_compare_func,
-        .free_value = bus_message_unref_wrapper,
-};
-
-int bus_message_append_string_set(sd_bus_message *m, Set *set) {
-        const char *s;
-        int r;
-
-        assert(m);
-
-        r = sd_bus_message_open_container(m, 'a', "s");
-        if (r < 0)
-                return r;
-
-        SET_FOREACH(s, set) {
-                r = sd_bus_message_append(m, "s", s);
-                if (r < 0)
-                        return r;
-        }
-
-        return sd_bus_message_close_container(m);
-}
-
-int bus_property_get_string_set(
-                sd_bus *bus,
-                const char *path,
-                const char *interface,
-                const char *property,
-                sd_bus_message *reply,
-                void *userdata,
-                sd_bus_error *error) {
-
-        Set **s = ASSERT_PTR(userdata);
-
-        assert(bus);
-        assert(property);
-        assert(reply);
-
-        return bus_message_append_string_set(reply, *s);
-}
-
 int bus_creds_get_pidref(
                 sd_bus_creds *c,
                 PidRef *ret) {
@@ -953,32 +905,27 @@ int bus_query_sender_pidref(
         return bus_creds_get_pidref(creds, ret);
 }
 
-int bus_message_read_id128(sd_bus_message *m, sd_id128_t *ret) {
-        const void *a;
-        size_t sz;
+int bus_get_instance_id(sd_bus *bus, sd_id128_t *ret) {
+        _cleanup_(sd_bus_message_unrefp) sd_bus_message *reply = NULL;
         int r;
 
-        assert(m);
+        assert(bus);
+        assert(ret);
 
-        r = sd_bus_message_read_array(m, 'y', &a, &sz);
+        r = sd_bus_call_method(bus,
+                               "org.freedesktop.DBus", "/org/freedesktop/DBus", "org.freedesktop.DBus", "GetId",
+                               /* error = */ NULL, &reply,
+                               NULL);
         if (r < 0)
                 return r;
 
-        switch (sz) {
-        case 0:
-                if (ret)
-                        *ret = SD_ID128_NULL;
-                return 0;
+        const char *id;
 
-        case sizeof(sd_id128_t):
-                if (ret)
-                        memcpy(ret, a, sz);
-                return !memeqzero(a, sz); /* This mimics sd_id128_is_null(), but ret may be NULL,
-                                           * and a may be misaligned, so use memeqzero() here. */
+        r = sd_bus_message_read_basic(reply, 's', &id);
+        if (r < 0)
+                return r;
 
-        default:
-                return -EINVAL;
-        }
+        return sd_id128_from_string(id, ret);
 }
 
 static const char* const bus_transport_table[] = {
diff --git a/src/shared/bus-util.h b/src/shared/bus-util.h
index 95b9adb7b1..63c3ba5ee3 100644
--- a/src/shared/bus-util.h
+++ b/src/shared/bus-util.h
@@ -65,7 +65,7 @@ static inline int bus_log_connect_error(int r, BusTransport transport, RuntimeSc
 int bus_path_encode_unique(sd_bus *b, const char *prefix, const char *sender_id, const char *external_id, char **ret_path);
 int bus_path_decode_unique(const char *path, const char *prefix, char **ret_sender, char **ret_external);
 
-int bus_track_add_name_many(sd_bus_track *t, char **l);
+int bus_track_add_name_many(sd_bus_track *t, char * const *l);
 int bus_track_to_strv(sd_bus_track *t, char ***ret);
 
 int bus_open_system_watch_bind_with_description(sd_bus **ret, const char *description);
@@ -78,15 +78,9 @@ int bus_reply_pair_array(sd_bus_message *m, char **l);
 /* Listen to GetMallocInfo() calls to 'destination' and return malloc_info() via FD */
 int bus_register_malloc_status(sd_bus *bus, const char *destination);
 
-extern const struct hash_ops bus_message_hash_ops;
-
-int bus_message_append_string_set(sd_bus_message *m, Set *s);
-
-int bus_property_get_string_set(sd_bus *bus, const char *path, const char *interface, const char *property, sd_bus_message *reply, void *userdata, sd_bus_error *error);
-
 int bus_creds_get_pidref(sd_bus_creds *c, PidRef *ret);
 int bus_query_sender_pidref(sd_bus_message *m, PidRef *ret);
 
-int bus_message_read_id128(sd_bus_message *m, sd_id128_t *ret);
+int bus_get_instance_id(sd_bus *bus, sd_id128_t *ret);
 
 const char* bus_transport_to_string(BusTransport transport) _const_;
diff --git a/src/shared/serialize.c b/src/shared/serialize.c
index 4d9ee6cc32..425e7f1ac3 100644
--- a/src/shared/serialize.c
+++ b/src/shared/serialize.c
@@ -164,11 +164,14 @@ int serialize_dual_timestamp(FILE *f, const char *name, const dual_timestamp *t)
         return serialize_item_format(f, name, USEC_FMT " " USEC_FMT, t->realtime, t->monotonic);
 }
 
-int serialize_strv(FILE *f, const char *key, char **l) {
+int serialize_strv(FILE *f, const char *key, char * const *l) {
         int ret = 0, r;
 
         /* Returns the first error, or positive if anything was serialized, 0 otherwise. */
 
+        assert(f);
+        assert(key);
+
         STRV_FOREACH(i, l) {
                 r = serialize_item_escaped(f, key, *i);
                 if ((ret >= 0 && r < 0) ||
@@ -179,6 +182,16 @@ int serialize_strv(FILE *f, const char *key, char **l) {
         return ret;
 }
 
+int serialize_id128(FILE *f, const char *key, sd_id128_t id) {
+        assert(f);
+        assert(key);
+
+        if (sd_id128_is_null(id))
+                return 0;
+
+        return serialize_item_format(f, key, SD_ID128_FORMAT_STR, SD_ID128_FORMAT_VAL(id));
+}
+
 int serialize_pidref(FILE *f, FDSet *fds, const char *key, PidRef *pidref) {
         int r;
 
@@ -267,8 +280,7 @@ int serialize_item_base64mem(FILE *f, const char *key, const void *p, size_t l)
         return 1;
 }
 
-int serialize_string_set(FILE *f, const char *key, Set *s) {
-        const char *e;
+int serialize_string_set(FILE *f, const char *key, const Set *s) {
         int r;
 
         assert(f);
@@ -279,6 +291,7 @@ int serialize_string_set(FILE *f, const char *key, Set *s) {
 
         /* Serialize as individual items, as each element might contain separators and escapes */
 
+        const char *e;
         SET_FOREACH(e, s) {
                 r = serialize_item(f, key, e);
                 if (r < 0)
diff --git a/src/shared/serialize.h b/src/shared/serialize.h
index dc753465c4..b573e6cc15 100644
--- a/src/shared/serialize.h
+++ b/src/shared/serialize.h
@@ -3,6 +3,8 @@
 
 #include <stdio.h>
 
+#include "sd-id128.h"
+
 #include "fdset.h"
 #include "image-policy.h"
 #include "macro.h"
@@ -21,10 +23,11 @@ int serialize_fd(FILE *f, FDSet *fds, const char *key, int fd);
 int serialize_fd_many(FILE *f, FDSet *fds, const char *key, const int fd_array[], size_t n_fd_array);
 int serialize_usec(FILE *f, const char *key, usec_t usec);
 int serialize_dual_timestamp(FILE *f, const char *key, const dual_timestamp *t);
-int serialize_strv(FILE *f, const char *key, char **l);
+int serialize_strv(FILE *f, const char *key, char * const *l);
+int serialize_id128(FILE *f, const char *key, sd_id128_t id);
 int serialize_pidref(FILE *f, FDSet *fds, const char *key, PidRef *pidref);
 int serialize_ratelimit(FILE *f, const char *key, const RateLimit *rl);
-int serialize_string_set(FILE *f, const char *key, Set *s);
+int serialize_string_set(FILE *f, const char *key, const Set *s);
 int serialize_image_policy(FILE *f, const char *key, const ImagePolicy *p);
 
 static inline int serialize_bool(FILE *f, const char *key, bool b) {
diff --git a/src/systemctl/systemctl-list-units.c b/src/systemctl/systemctl-list-units.c
index a2f3074358..b7cb103513 100644
--- a/src/systemctl/systemctl-list-units.c
+++ b/src/systemctl/systemctl-list-units.c
@@ -5,6 +5,7 @@
 #include "ansi-color.h"
 #include "bus-error.h"
 #include "bus-locator.h"
+#include "bus-message-util.h"
 #include "format-table.h"
 #include "locale-util.h"
 #include "path-util.h"
diff --git a/src/timedate/timedated.c b/src/timedate/timedated.c
index c79bb864df..b196034a25 100644
--- a/src/timedate/timedated.c
+++ b/src/timedate/timedated.c
@@ -17,6 +17,7 @@
 #include "bus-locator.h"
 #include "bus-log-control-api.h"
 #include "bus-map-properties.h"
+#include "bus-message-util.h"
 #include "bus-polkit.h"
 #include "bus-unit-util.h"
 #include "clock-util.h"