diff --git a/core/kernel_init.c b/core/kernel_init.c
index 29122abe0a..eb35ea5feb 100644
--- a/core/kernel_init.c
+++ b/core/kernel_init.c
@@ -37,7 +37,7 @@ volatile tcb_t *sched_threads[MAXTHREADS];
 volatile tcb_t *active_thread;
 volatile int lpm_prevent_sleep = 0;
 
-extern void main(void);
+extern int main(void);
 
 static void idle_thread(void) {
     while(1) {
diff --git a/sys/auto_init/auto_init.c b/sys/auto_init/auto_init.c
index be6feabada..6c084af3e9 100644
--- a/sys/auto_init/auto_init.c
+++ b/sys/auto_init/auto_init.c
@@ -9,7 +9,7 @@
 #define ENABLE_DEBUG
 #include <debug.h>
 
-extern void main(void);
+extern int main(void);
 
 void auto_init(void) {
 #ifdef MODULE_BOARD_DISPLAY