diff --git a/Backends/Graphics4/OpenGL/Sources/kinc/backend/graphics4/constantbuffer.h b/Backends/Graphics4/OpenGL/Sources/kinc/backend/graphics4/constantbuffer.h
index 8177f3f31..67f25c535 100644
--- a/Backends/Graphics4/OpenGL/Sources/kinc/backend/graphics4/constantbuffer.h
+++ b/Backends/Graphics4/OpenGL/Sources/kinc/backend/graphics4/constantbuffer.h
@@ -2,6 +2,8 @@
 
 #ifdef KINC_KONG
 
+#include <stddef.h>
+
 typedef struct kinc_g4_constant_buffer_impl {
 	unsigned buffer;
 	void *data;