diff --git a/reactos/include/crt/sec_api/io_s.h b/reactos/include/crt/sec_api/io_s.h
index ec565a61714..c83f0846ab6 100644
--- a/reactos/include/crt/sec_api/io_s.h
+++ b/reactos/include/crt/sec_api/io_s.h
@@ -3,6 +3,7 @@
  * This file is part of the w64 mingw-runtime package.
  * No warranty is given; refer to the file DISCLAIMER within this package.
  */
+
 #ifndef _INC_IO_S
 #define _INC_IO_S
 
@@ -14,20 +15,62 @@
 extern "C" {
 #endif
 
-  _CRTIMP errno_t __cdecl _access_s(const char *_Filename,int _AccessMode);
-  _CRTIMP errno_t __cdecl _chsize_s(int _FileHandle,__int64 _Size);
-  _CRTIMP errno_t __cdecl _mktemp_s(char *_TemplateName,size_t _Size);
-  _CRTIMP errno_t __cdecl _umask_s(int _NewMode,int *_OldMode);
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _access_s(
+    _In_z_ const char *_Filename,
+    _In_ int _AccessMode);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _chsize_s(
+    _In_ int _FileHandle,
+    _In_ __int64 _Size);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _mktemp_s(
+    _Inout_updates_z_(_Size) char *_TemplateName,
+    _In_ size_t _Size);
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _umask_s(
+    _In_ int _NewMode,
+    _Out_ int *_OldMode);
 
 #ifndef _WIO_S_DEFINED
 #define _WIO_S_DEFINED
-  _CRTIMP errno_t __cdecl _waccess_s(const wchar_t *_Filename,int _AccessMode);
-  _CRTIMP errno_t __cdecl _wmktemp_s(wchar_t *_TemplateName,size_t _SizeInWords);
-#endif
+
+  _Check_return_wat_
+  _CRTIMP
+  errno_t
+  __cdecl
+  _waccess_s(
+    _In_z_ const wchar_t *_Filename,
+    _In_ int _AccessMode);
+
+  _CRTIMP
+  errno_t
+  __cdecl
+  _wmktemp_s(
+    _Inout_updates_z_(_SizeInWords) wchar_t *_TemplateName,
+    _In_ size_t _SizeInWords);
+
+#endif /* _WIO_S_DEFINED */
 
 #ifdef __cplusplus
 }
 #endif
 
-#endif
-#endif
+#endif /* MINGW_HAS_SECURE_API */
+
+#endif /* _INC_IO_S */