diff --git a/main.c b/main.c
index 29a00a3..14a2b8d 100644
--- a/main.c
+++ b/main.c
@@ -1,3 +1,4 @@
+#include "libopencm3/cm3/vector.h"
 #include "system.h"
 #include "timer.h"
 #include "uart.h"
@@ -56,9 +57,10 @@ int main(void) {
     while (sys_ticks_get() == init);
 
     uint64_t ref = 0;
-    while (1) {
+    for (int i = 0; i < 20;) {
         if (sys_ticks_get() > ref) {
             ref += 500;
+            i++;
             gpio_toggle(GPIOC, GPIO13);
         }
     }