diff --git a/sockcompat.c b/sockcompat.c
index f99d14b..ca1bacc 100644
--- a/sockcompat.c
+++ b/sockcompat.c
@@ -32,6 +32,7 @@
 #include "sockcompat.h"
 
 #ifdef _WIN32
+#include <errno.h>
 static int _wsaErrorToErrno(int err) {
     switch (err) {
         case WSAEWOULDBLOCK: