diff --git a/compat/mingw.h b/compat/mingw.h
index bd0a88bc1d1..6b531e4013c 100644
--- a/compat/mingw.h
+++ b/compat/mingw.h
@@ -32,7 +32,9 @@ typedef int socklen_t;
 #define WEXITSTATUS(x) ((x) & 0xff)
 #define WTERMSIG(x) SIGTERM
 
+#ifndef EWOULDBLOCK
 #define EWOULDBLOCK EAGAIN
+#endif
 #define SHUT_WR SD_SEND
 
 #define SIGHUP 1
@@ -46,8 +48,12 @@ typedef int socklen_t;
 #define F_SETFD 2
 #define FD_CLOEXEC 0x1
 
+#ifndef EAFNOSUPPORT
 #define EAFNOSUPPORT WSAEAFNOSUPPORT
+#endif
+#ifndef ECONNABORTED
 #define ECONNABORTED WSAECONNABORTED
+#endif
 
 struct passwd {
 	char *pw_name;