diff --git a/lib/idn.c b/lib/idn.c
index 798c9aaef1..12fa5bbf11 100644
--- a/lib/idn.c
+++ b/lib/idn.c
@@ -152,8 +152,8 @@ static CURLcode mac_ascii_to_idn(const char *in, char **out)
 #ifdef USE_WIN32_IDN
 /* using Windows kernel32 and normaliz libraries. */
 
-#if (!defined(_WIN32_WINNT) || _WIN32_WINNT < 0x600) && \
-  (!defined(WINVER) || WINVER < 0x600)
+#if (!defined(_WIN32_WINNT) || _WIN32_WINNT < _WIN32_WINNT_VISTA) && \
+  (!defined(WINVER) || WINVER < _WIN32_WINNT_VISTA)
 WINBASEAPI int WINAPI IdnToAscii(DWORD dwFlags,
                                  const WCHAR *lpUnicodeCharStr,
                                  int cchUnicodeChar,
diff --git a/lib/rand.c b/lib/rand.c
index 72545e0867..4bff30d677 100644
--- a/lib/rand.c
+++ b/lib/rand.c
@@ -48,7 +48,7 @@
 
 #ifdef _WIN32
 
-#if defined(_WIN32_WINNT) && _WIN32_WINNT >= 0x600 && \
+#if defined(_WIN32_WINNT) && _WIN32_WINNT >= _WIN32_WINNT_VISTA && \
   !defined(CURL_WINDOWS_UWP)
 #  define HAVE_WIN_BCRYPTGENRANDOM
 #  include <bcrypt.h>