diff --git a/main/heartbeat/heartbeat.c b/main/heartbeat/heartbeat.c
index e680201..b5931db 100644
--- a/main/heartbeat/heartbeat.c
+++ b/main/heartbeat/heartbeat.c
@@ -3,6 +3,7 @@
 #include "bus/message_bus.h"
 
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 #include <stdbool.h>
 #include <ctype.h>