diff --git a/ext/socket/mkconstants.rb b/ext/socket/mkconstants.rb
index ba7a55b4266b61..f8def9f990352a 100644
--- a/ext/socket/mkconstants.rb
+++ b/ext/socket/mkconstants.rb
@@ -762,6 +762,7 @@ def def_intern(func_name, pat, prefix_optional=nil)
 IPV6_PATHMTU	nil	Retrieve current path MTU
 IPV6_PKTINFO	nil	Receive packet information with datagram
 IPV6_RECVDSTOPTS	nil	Receive all IP6 options for response
+IPV6_RECVERR	nil	Enable extended reliable error message passing
 IPV6_RECVHOPLIMIT	nil	Receive hop limit with datagram
 IPV6_RECVHOPOPTS	nil	Receive hop-by-hop options
 IPV6_RECVPKTINFO	nil	Receive destination IP address and incoming interface