diff --git a/ChangeLog b/ChangeLog
index e6dc78116..40be94cb9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -12,6 +12,8 @@ Bugfix
      TrinityTonic. #1359.
    * Fix an issue with MicroBlaze support in bn_mul.h which was causing the
      build to fail. Found by zv-io. Fixes #1651.
+   * Fix for redefinition of _WIN32_WINNT to avoid overriding a definition
+     used by user applications. Found and fixed by Fabio Alessandrelli.
 
 Changes
    * Support TLS testing in out-of-source builds using cmake.
diff --git a/library/net.c b/library/net.c
index e3aa2a993..e8123cc81 100644
--- a/library/net.c
+++ b/library/net.c
@@ -34,11 +34,12 @@
 #if (defined(_WIN32) || defined(_WIN32_WCE)) && !defined(EFIX64) && \
     !defined(EFI32)
 
-#ifdef _WIN32_WINNT
+#if !defined(_WIN32_WINNT) || (_WIN32_WINNT < 0x0501)
 #undef _WIN32_WINNT
-#endif
 /* Enables getaddrinfo() & Co */
 #define _WIN32_WINNT 0x0501
+#endif
+
 #include <ws2tcpip.h>
 
 #include <winsock2.h>