diff --git a/crc32_vmull.c b/crc32_vmull.c
index fd88cd6..2f965fb 100644
--- a/crc32_vmull.c
+++ b/crc32_vmull.c
@@ -6,6 +6,7 @@
 
 #include <arm_neon.h>
 #include <stdint.h>
+#include <stddef.h>
 
 #include "library.h"
 #include "crc32.h"
diff --git a/crc64_vmull.c b/crc64_vmull.c
index c89acdf..611f13e 100644
--- a/crc64_vmull.c
+++ b/crc64_vmull.c
@@ -6,6 +6,7 @@
 
 #include <arm_neon.h>
 #include <stdint.h>
+#include <stddef.h>
 
 #include "library.h"
 #include "arm_vmull.h"