diff --git a/libavformat/network.h b/libavformat/network.h
index 9f7b78202e..191c00891f 100644
--- a/libavformat/network.h
+++ b/libavformat/network.h
@@ -31,9 +31,21 @@
 #include <winsock2.h>
 #include <ws2tcpip.h>
 
+#ifdef EPROTONOSUPPORT
+# undef EPROTONOSUPPORT
+#endif
 #define EPROTONOSUPPORT WSAEPROTONOSUPPORT
+#ifdef ETIMEDOUT
+# undef ETIMEDOUT
+#endif
 #define ETIMEDOUT       WSAETIMEDOUT
+#ifdef ECONNREFUSED
+# undef ECONNREFUSED
+#endif
 #define ECONNREFUSED    WSAECONNREFUSED
+#ifdef EINPROGRESS
+# undef EINPROGRESS
+#endif
 #define EINPROGRESS     WSAEINPROGRESS
 
 int ff_neterrno(void);
diff --git a/libavformat/os_support.h b/libavformat/os_support.h
index fca5b2a813..159d4d7f85 100644
--- a/libavformat/os_support.h
+++ b/libavformat/os_support.h
@@ -31,6 +31,9 @@
 
 #if defined(__MINGW32__) && !defined(__MINGW32CE__)
 #  include <fcntl.h>
+#  ifdef lseek
+#   undef lseek
+#  endif
 #  define lseek(f,p,w) _lseeki64((f), (p), (w))
 #  define stat _stati64
 #  define fstat(f,s) _fstati64((f), (s))