diff --git a/src/libavrdude.h b/src/libavrdude.h
index 413be677..1675b766 100644
--- a/src/libavrdude.h
+++ b/src/libavrdude.h
@@ -24,6 +24,7 @@
 #include <stdio.h>
 #include <limits.h>
 #include <stdbool.h>
+#include <stddef.h>
 #include <stdint.h>
 
 #ifdef LIBAVRDUDE_INCLUDE_INTERNAL_HEADERS