--- a/src-IL/include/il_exr.h
+++ b/src-IL/include/il_exr.h
@@ -16,6 +16,7 @@

 #include "il_internal.h"
 #include <ImfIO.h>
+#include <ImfInt64.h>


 //using namespace Imf;  // Using this leads to errors with Microsoft's IStream.