diff --git a/direct/src/plugin/get_twirl_data.h b/direct/src/plugin/get_twirl_data.h
index 083ba81d50..31bb16c29c 100755
--- a/direct/src/plugin/get_twirl_data.h
+++ b/direct/src/plugin/get_twirl_data.h
@@ -15,6 +15,8 @@
 #ifndef GET_TWIRL_DATA_H
 #define GET_TWIRL_DATA_H
 
+#include "stddef.h"
+
 static const int twirl_width = 48;
 static const int twirl_height = 48;
 static const int twirl_num_steps = 12;