diff --git a/tlib/include/tlib/system.hpp b/tlib/include/tlib/system.hpp
index 0f24627a..ce3338c7 100644
--- a/tlib/include/tlib/system.hpp
+++ b/tlib/include/tlib/system.hpp
@@ -31,8 +31,8 @@ void sleep_ms(size_t ms);
 
 datetime local_date();
 
-void reboot(unsigned int);
-void shutdown(unsigned int);
+void reboot(unsigned int delay = 0);
+void shutdown(unsigned int delay = 0);
 
 uint64_t s_time();
 uint64_t ms_time();