diff --git a/src/microsoft/compiler/dxil_validator.h b/src/microsoft/compiler/dxil_validator.h
index 0a880eb155d..de5c064b711 100644
--- a/src/microsoft/compiler/dxil_validator.h
+++ b/src/microsoft/compiler/dxil_validator.h
@@ -24,6 +24,8 @@
 #ifndef DXIL_VALIDATOR_H
 #define DXIL_VALIDATOR_H
 
+#include <stddef.h>
+
 struct dxil_validator;
 
 #ifdef __cplusplus