diff --git a/lib/posix/posix.nim b/lib/posix/posix.nim
index 0c66aa2b94..175f6a61dd 100644
--- a/lib/posix/posix.nim
+++ b/lib/posix/posix.nim
@@ -823,6 +823,12 @@ proc CMSG_NXTHDR*(mhdr: ptr Tmsghdr, cmsg: ptr Tcmsghdr): ptr Tcmsghdr {.
 proc CMSG_FIRSTHDR*(mhdr: ptr Tmsghdr): ptr Tcmsghdr {.
   importc, header: "<sys/socket.h>".}
 
+proc CMSG_SPACE*(len: csize): csize {.
+  importc, header: "<sys/socket.h>".}
+
+proc CMSG_LEN*(len: csize): csize {.
+  importc, header: "<sys/socket.h>".}
+
 const
   INVALID_SOCKET* = SocketHandle(-1)