diff --git a/c/fdpass.c b/c/fdpass.c
index b54df7d..95aa58a 100644
--- a/c/fdpass.c
+++ b/c/fdpass.c
@@ -1,6 +1,10 @@
 /* File descriptor passing based on
  *   https://manned.org/man.c2c6968a/cmsg.3 */
 
+#ifndef MSG_CMSG_CLOEXEC
+#define MSG_CMSG_CLOEXEC 0
+#endif
+
 static ssize_t fufdpass_send(int socket, int fd, const char *buf, size_t buflen) {
     union {
         char buf[CMSG_SPACE(sizeof(int))];