diff --git a/libfreedv/codec2_fft.h b/libfreedv/codec2_fft.h
index 8651c24fb..56f1ae422 100644
--- a/libfreedv/codec2_fft.h
+++ b/libfreedv/codec2_fft.h
@@ -13,6 +13,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <math.h>
+#include <cstddef>
 
 #include "codec2/comp.h"
 #include "defines.h"