diff --git a/src/wspr.c b/src/wspr.c
--- a/src/wspr.c
+++ b/src/wspr.c
@@ -3,6 +3,7 @@
 #include "jtencode.h"
 #include "gpio.h"
 #include "wspr.h"
+#include "i2c.h"
 #include "config.h"