diff --git a/lib/setup.h b/lib/setup.h
index 11e137fc2..fe1613c11 100644
--- a/lib/setup.h
+++ b/lib/setup.h
@@ -166,6 +166,17 @@ defined(HAVE_LIBSSL) && defined(HAVE_LIBCRYPTO)
 #define WIN32_LEAN_AND_MEAN  /* Prevent including <winsock*.h> in <windows.h> */
 #endif
 
+#if (defined(ENABLE_IPV6) || defined(CURLDEBUG)) && defined(_MSC_VER) && \
+    (!defined(_WIN32_WINNT) || _WIN32_WINNT < 0x0500)
+/*
+ * Needed to pull in the real getaddrinfo() and not the inline version
+ * in <wspiAPI.H> which doesn't support IPv6 (IPv4 only). <wspiAPI.H> is
+ * included from <ws2tcpip.h> for <= 0x0500 SDKs.
+ */
+#undef  _WIN32_WINNT
+#define _WIN32_WINNT 0x0501
+#endif
+
 #include <winsock2.h>        /* required by telnet.c */
 
 #if defined(ENABLE_IPV6) || defined(USE_SSLEAY)