diff --git a/handler/win/wer/crashpad_wer.cc b/handler/win/wer/crashpad_wer.cc
index 1394e20..1973e7f 100644
--- a/handler/win/wer/crashpad_wer.cc
+++ b/handler/win/wer/crashpad_wer.cc
@@ -20,6 +20,7 @@
 #include "util/misc/address_types.h"
 #include "util/win/registration_protocol_win_structs.h"
 
+#include <stddef.h>
 #include <Windows.h>
 #include <werapi.h>