diff --git a/configure.ac b/configure.ac
index 3d6a6cfb045a85dd9bad9265b6384335dc9739c1..6e25605e10633fd9242e8f6653f4ceb19305d2c5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -609,6 +609,7 @@ AC_CHECK_TYPES([struct pollfd],,,
 #if HAVE_POLL
 # include <poll.h>
 #elif defined (_WIN32)
+# define _WIN32_WINNT 0x502
 # include <winsock2.h>
 #endif
 ])