diff --git a/sys/riotboot/flashwrite.c b/sys/riotboot/flashwrite.c
index 2a968da5cd..148b882f08 100644
--- a/sys/riotboot/flashwrite.c
+++ b/sys/riotboot/flashwrite.c
@@ -20,6 +20,7 @@
  * @}
  */
 
+#include <assert.h>
 #include <string.h>
 
 #include "riotboot/flashwrite.h"