diff --git a/tests/d3d12_crosstest.h b/tests/d3d12_crosstest.h
index 43af375b..0b77bdee 100644
--- a/tests/d3d12_crosstest.h
+++ b/tests/d3d12_crosstest.h
@@ -52,6 +52,7 @@ typedef int HRESULT;
 #include <inttypes.h>
 #include <limits.h>
 #include <math.h>
+#include <stddef.h>
 #include <time.h>
 
 #ifdef _WIN32