diff --git a/tests/unit-test-server.c b/tests/unit-test-server.c
index 54f7d2d26..5c223ea56 100644
--- a/tests/unit-test-server.c
+++ b/tests/unit-test-server.c
@@ -21,7 +21,11 @@
 #include <stdlib.h>
 #include <errno.h>
 #include <modbus.h>
-#include <sys/socket.h>
+#ifdef _WIN32
+# include <winsock2.h>
+#else
+# include <sys/socket.h>
+#endif
 
 #include "unit-test.h"