diff --git a/src/cw/format.c b/src/cw/format.c
index b804a7b9..704ffe4d 100644
--- a/src/cw/format.c
+++ b/src/cw/format.c
@@ -25,6 +25,8 @@
 #include <stdint.h>
 #include <stdio.h>
 
+#include "cw.h"
+
 /**
  * Format bytes as hex string.
  * @param dst Destination buffer