diff --git a/ssl_verify.h b/ssl_verify.h
index 067762b..8a349b6 100644
--- a/ssl_verify.h
+++ b/ssl_verify.h
@@ -29,7 +29,10 @@
 #include <openssl/x509.h>
 #include <openssl/ssl.h>
 #include <openssl/err.h>
+#ifdef X509_NAME
+/* wincrypt.h has already a different define... */
 #undef X509_NAME
+#endif
 #include <openssl/x509v3.h>
 
 #ifdef __cplusplus