diff --git a/dbus/dbus-sysdeps-unix.c b/dbus/dbus-sysdeps-unix.c
index 5d9c404f..1c72327f 100644
--- a/dbus/dbus-sysdeps-unix.c
+++ b/dbus/dbus-sysdeps-unix.c
@@ -2348,7 +2348,8 @@ _dbus_poll (DBusPollFD *fds,
 }
 
 /**
- * Get current time, as in gettimeofday().
+ * Get current time, as in gettimeofday(). Use the monotonic clock if
+ * available, to avoid problems when the system time changes.
  *
  * @param tv_sec return location for number of seconds
  * @param tv_usec return location for number of microseconds (thousandths)
@@ -2359,12 +2360,22 @@ _dbus_get_current_time (long *tv_sec,
 {
   struct timeval t;
 
+#ifdef HAVE_MONOTONIC_CLOCK
+  struct timespec ts;
+  clock_gettime (CLOCK_MONOTONIC, &ts);
+
+  if (tv_sec)
+    *tv_sec = ts.tv_sec;
+  if (tv_usec)
+    *tv_usec = ts.tv_nsec / 1000;
+#else
   gettimeofday (&t, NULL);
 
   if (tv_sec)
     *tv_sec = t.tv_sec;
   if (tv_usec)
     *tv_usec = t.tv_usec;
+#endif
 }
 
 /**
diff --git a/dbus/dbus-userdb.c b/dbus/dbus-userdb.c
index 5a153c6a..bfa4c435 100644
--- a/dbus/dbus-userdb.c
+++ b/dbus/dbus-userdb.c
@@ -226,7 +226,8 @@ static DBusString process_homedir;
 static void
 shutdown_system_db (void *data)
 {
-  _dbus_user_database_unref (system_db);
+  if (system_db != NULL)
+    _dbus_user_database_unref (system_db);
   system_db = NULL;
   _dbus_string_free (&process_username);
   _dbus_string_free (&process_homedir);
@@ -345,7 +346,8 @@ _dbus_user_database_flush_system (void)
 {
   _dbus_user_database_lock_system ();
    
-  _dbus_user_database_flush (system_db);
+   if (system_db != NULL)
+    _dbus_user_database_flush (system_db);
 
   _dbus_user_database_unlock_system ();
 }