diff --git a/lib/wsprd/nhash.h b/lib/wsprd/nhash.h
index 096ade65e..d13268d9e 100644
--- a/lib/wsprd/nhash.h
+++ b/lib/wsprd/nhash.h
@@ -4,6 +4,7 @@
 #ifdef Win32
 #include "win_stdint.h"	/* defines uint32_t etc */
 #else
+#include <stddef.h>
 #include <stdint.h>	/* defines uint32_t etc */
 #endif