diff --git a/rostests/apitests/com/com_apitest.h b/rostests/apitests/com/com_apitest.h
index 3ba030d4def..85bbd65537a 100644
--- a/rostests/apitests/com/com_apitest.h
+++ b/rostests/apitests/com/com_apitest.h
@@ -36,7 +36,6 @@
 #include <ndk/rtlfuncs.h>
 #include <initguid.h>
 
-#define RTL_NUMBER_OF(x) (sizeof(x) / sizeof(x[0]))
 typedef IUnknown *PUNKNOWN;
 
 typedef struct _CLASS_AND_INTERFACES