diff --git a/src/PlatformSockets.h b/src/PlatformSockets.h
index 3f5b613..ce65b52 100644
--- a/src/PlatformSockets.h
+++ b/src/PlatformSockets.h
@@ -12,10 +12,34 @@
 #define LastSocketError() WSAGetLastError()
 
 #define SHUT_RDWR SD_BOTH
+
+// errno.h will include incompatible definitions of these
+// values compared to what Winsock uses, so we must undef
+// them to ensure the correct value is used.
+
+#ifdef EWOULDBLOCK
+#undef EWOULDBLOCK
+#endif
 #define EWOULDBLOCK WSAEWOULDBLOCK
+
+#ifdef EAGAIN
+#undef EAGAIN
+#endif
 #define EAGAIN WSAEWOULDBLOCK
+
+#ifdef EINPROGRESS
+#undef EINPROGRESS
+#endif
 #define EINPROGRESS WSAEINPROGRESS
+
+#ifdef EINTR
+#undef EINTR
+#endif
 #define EINTR WSAEINTR
+
+#ifdef ETIMEDOUT
+#undef ETIMEDOUT
+#endif
 #define ETIMEDOUT WSAETIMEDOUT
 
 typedef int SOCK_RET;