diff --git a/mingw-w64-headers/include/propsys.h b/mingw-w64-headers/include/propsys.h
index ff1ca98..9427fde 100644
--- a/mingw-w64-headers/include/propsys.h
+++ b/mingw-w64-headers/include/propsys.h
@@ -10,6 +10,11 @@
 
 #undef  INTERFACE
 #define INTERFACE IPropertyStore
+#ifdef __GNUC__
+#warning COM interfaces layout in this header has not been verified.
+#warning COM interfaces with incorrect layout may not work at all.
+__MINGW_BROKEN_INTERFACE(INTERFACE)
+#endif
 DECLARE_INTERFACE_(IPropertyStore,IUnknown)
 {
     BEGIN_INTERFACE
@@ -41,6 +46,11 @@
 
 #undef  INTERFACE
 #define INTERFACE INamedPropertyStore
+#ifdef __GNUC__
+#warning COM interfaces layout in this header has not been verified.
+#warning COM interfaces with incorrect layout may not work at all.
+__MINGW_BROKEN_INTERFACE(INTERFACE)
+#endif
 DECLARE_INTERFACE_(INamedPropertyStore,IUnknown)
 {
     BEGIN_INTERFACE