diff --git a/mqtt_client.c b/mqtt_client.c
index 01e3d74..57a8bfc 100644
--- a/mqtt_client.c
+++ b/mqtt_client.c
@@ -1,4 +1,5 @@
 #include <stdio.h>
+#include <stdlib.h>
 #include "esp_err.h"
 #include "platform.h"