if (BUS_MESSAGE_COOKIE(m) == 0xFFFFFFFFULL)
                         fprintf(f, " Cookie=-1");
                 else
-                        fprintf(f, " Cookie=%lu", (unsigned long) BUS_MESSAGE_COOKIE(m));
+                        fprintf(f, " Cookie=%" PRIu64, BUS_MESSAGE_COOKIE(m));
 
                 if (m->reply_cookie != 0)
-                        fprintf(f, "  ReplyCookie=%lu", (unsigned long) m->reply_cookie);
+                        fprintf(f, "  ReplyCookie=%" PRIu64, m->reply_cookie);
 
                 fputs("\n", f);
 
 
                 well_known ? 0 :
                 m->destination ? unique : KDBUS_DST_ID_BROADCAST;
         m->kdbus->payload_type = KDBUS_PAYLOAD_DBUS;
-        m->kdbus->cookie = m->header->serial;
+        m->kdbus->cookie = (uint64_t) m->header->serial;
         m->kdbus->priority = m->priority;
 
         if (m->header->flags & BUS_MESSAGE_NO_REPLY_EXPECTED)
 
         t->header->flags |= BUS_MESSAGE_NO_REPLY_EXPECTED;
         t->reply_cookie = BUS_MESSAGE_COOKIE(call);
 
-        r = message_append_field_uint32(t, BUS_MESSAGE_HEADER_REPLY_SERIAL, t->reply_cookie);
+        r = message_append_field_uint32(t, BUS_MESSAGE_HEADER_REPLY_SERIAL, (uint32_t) t->reply_cookie);
         if (r < 0)
                 goto fail;
 
         t->header->flags |= BUS_MESSAGE_NO_REPLY_EXPECTED;
         t->reply_cookie = cookie;
 
-        r = message_append_field_uint32(t, BUS_MESSAGE_HEADER_REPLY_SERIAL, t->reply_cookie);
+        r = message_append_field_uint32(t, BUS_MESSAGE_HEADER_REPLY_SERIAL, (uint32_t) t->reply_cookie);
         if (r < 0)
                 goto fail;
 
                         break;
                 }
 
-                case BUS_MESSAGE_HEADER_REPLY_SERIAL:
+                case BUS_MESSAGE_HEADER_REPLY_SERIAL: {
+                        uint32_t serial;
+
                         if (m->reply_cookie != 0)
                                 return -EBADMSG;
 
                         if (!streq(signature, "u"))
                                 return -EBADMSG;
 
-                        r = message_peek_field_uint32(m, &ri, item_size, &m->reply_cookie);
+                        r = message_peek_field_uint32(m, &ri, item_size, &serial);
                         if (r < 0)
                                 return r;
 
+                        m->reply_cookie = serial;
+
                         if (m->reply_cookie == 0)
                                 return -EBADMSG;
 
                         break;
+                }
 
                 case BUS_MESSAGE_HEADER_UNIX_FDS:
                         if (unix_fds != 0)
                         return -ENOMEM;
 
                 n->reply_cookie = (*m)->reply_cookie;
-                r = message_append_field_uint32(n, BUS_MESSAGE_HEADER_REPLY_SERIAL, n->reply_cookie);
+                r = message_append_field_uint32(n, BUS_MESSAGE_HEADER_REPLY_SERIAL, (uint32_t) n->reply_cookie);
                 if (r < 0)
                         return r;
 
 
 
         sd_bus *bus;
 
-        uint32_t reply_cookie;
+        uint64_t reply_cookie;
 
         const char *path;
         const char *interface;
         return BUS_MESSAGE_NEED_BSWAP(m) ? bswap_64(u) : u;
 }
 
-static inline uint32_t BUS_MESSAGE_COOKIE(sd_bus_message *m) {
+static inline uint64_t BUS_MESSAGE_COOKIE(sd_bus_message *m) {
+        /* Note that we return the serial converted to a 64bit value here */
         return BUS_MESSAGE_BSWAP32(m, m->header->serial);
 }
 
 
                 return r;
 
         if (bus->is_kernel || *idx >= BUS_MESSAGE_SIZE(m))
-                log_debug("Sent message type=%s sender=%s destination=%s object=%s interface=%s member=%s cookie=%lu reply_cookie=%lu error=%s",
+                log_debug("Sent message type=%s sender=%s destination=%s object=%s interface=%s member=%s cookie=%" PRIu64 " reply_cookie=%" PRIu64 " error=%s",
                           bus_message_type_to_string(m->header->type),
                           strna(sd_bus_message_get_sender(m)),
                           strna(sd_bus_message_get_destination(m)),
                           strna(sd_bus_message_get_path(m)),
                           strna(sd_bus_message_get_interface(m)),
                           strna(sd_bus_message_get_member(m)),
-                          (unsigned long) BUS_MESSAGE_COOKIE(m),
-                          (unsigned long) m->reply_cookie,
+                          BUS_MESSAGE_COOKIE(m),
+                          m->reply_cookie,
                           strna(m->error.message));
 
         return r;
         bus->current = m;
         bus->iteration_counter++;
 
-        log_debug("Got message type=%s sender=%s destination=%s object=%s interface=%s member=%s cookie=%lu reply_cookie=%lu error=%s",
+        log_debug("Got message type=%s sender=%s destination=%s object=%s interface=%s member=%s cookie=%" PRIu64 " reply_cookie=%" PRIu64 " error=%s",
                   bus_message_type_to_string(m->header->type),
                   strna(sd_bus_message_get_sender(m)),
                   strna(sd_bus_message_get_destination(m)),
                   strna(sd_bus_message_get_path(m)),
                   strna(sd_bus_message_get_interface(m)),
                   strna(sd_bus_message_get_member(m)),
-                  (unsigned long) BUS_MESSAGE_COOKIE(m),
-                  (unsigned long) m->reply_cookie,
+                  BUS_MESSAGE_COOKIE(m),
+                  m->reply_cookie,
                   strna(m->error.message));
 
         r = process_hello(bus, m);