diff --git a/src/core/stdafx.h b/src/core/stdafx.h
index edcc83a8..50520218 100644
--- a/src/core/stdafx.h
+++ b/src/core/stdafx.h
@@ -25,6 +25,13 @@
 
 #include "thirdparty/curl/include/curl/curl.h"
 
+// RapidJSON uses 32 bit size types. Size types are
+// 64 bit wide on our target. Override it with ours.
+// this must be done before the rapidjson.h include.
+#define RAPIDJSON_NO_SIZETYPEDEFINE
+namespace rapidjson { typedef ::std::size_t SizeType; }
+
+#include "rapidjson/rapidjson.h"
 #include "rapidjson/document.h"
 #include "rapidjson/writer.h"
 #include "rapidjson/stringbuffer.h"