diff --git a/src/clock.c b/src/clock.c
index 1bedb4e06a..4fa73da472 100644
--- a/src/clock.c
+++ b/src/clock.c
@@ -24,8 +24,6 @@
 static rt_tick_t rt_tick = 0;
 #endif
 
-extern void rt_timer_check(void);
-
 /**
  * This function will init system tick and set it to zero.
  * @ingroup SystemInit