diff --git a/include/stdex/compat.hpp b/include/stdex/compat.hpp
index 777fb2475..9b98e1c93 100644
--- a/include/stdex/compat.hpp
+++ b/include/stdex/compat.hpp
@@ -162,6 +162,10 @@
 #define _Null_terminated_
 #endif
 
+#ifndef _Acquires_lock_
+#define _Acquires_lock_(l)
+#endif
+
 #ifndef _L
 #define __L(x) L ## x
 #define _L(x)  __L(x)