diff --git a/sys/netinet/tcp_fastopen.c b/sys/netinet/tcp_fastopen.c
index ec02d18fada1..e2b3b8637f60 100644
--- a/sys/netinet/tcp_fastopen.c
+++ b/sys/netinet/tcp_fastopen.c
@@ -108,6 +108,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/limits.h>
 #include <sys/lock.h>
 #include <sys/rmlock.h>
+#include <sys/socket.h>
 #include <sys/socketvar.h>
 #include <sys/sysctl.h>
 #include <sys/systm.h>