diff --git a/drivers/include/periph/rtt.h b/drivers/include/periph/rtt.h
index 89f76f7496..54d58022f0 100644
--- a/drivers/include/periph/rtt.h
+++ b/drivers/include/periph/rtt.h
@@ -23,6 +23,8 @@
 #ifndef PERIPH_RTT_H
 #define PERIPH_RTT_H
 
+#include <stdint.h>
+
 #include "periph_conf.h"
 
 #ifdef __cplusplus