diff --git a/Drv/Ip/UdpSocket.hpp b/Drv/Ip/UdpSocket.hpp
index e065c1e20d..819a7450b2 100644
--- a/Drv/Ip/UdpSocket.hpp
+++ b/Drv/Ip/UdpSocket.hpp
@@ -26,6 +26,7 @@
 // These macros are defined somewhere in inetLib.h.
 #undef m_type
 #undef m_data
+#undef m_len
 
 #else
 #include <arpa/inet.h>