diff --git a/clang/test/SemaCXX/microsoft-new-delete.cpp b/clang/test/SemaCXX/microsoft-new-delete.cpp
index 90b42edb18f9..e0d25dcd86f7 100644
--- a/clang/test/SemaCXX/microsoft-new-delete.cpp
+++ b/clang/test/SemaCXX/microsoft-new-delete.cpp
@@ -1,8 +1,10 @@
 // RUN: %clang_cc1 -fms-compatibility -fsyntax-only -verify %s
 // expected-no-diagnostics
 
+#include <stddef.h>
+
 struct arbitrary_t {} arbitrary;
-void *operator new(unsigned int size, arbitrary_t);
+void *operator new(size_t size, arbitrary_t);
 
 void f() {
   // Expect no error in MSVC compatibility mode