diff --git a/sys/alpha/osf1/osf1_mount.c b/sys/alpha/osf1/osf1_mount.c
index 1591c1046577..1d0ac2a1356f 100644
--- a/sys/alpha/osf1/osf1_mount.c
+++ b/sys/alpha/osf1/osf1_mount.c
@@ -47,6 +47,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/malloc.h>
 #include <sys/mount.h>
 #include <sys/proc.h>
+#include <sys/jail.h>
 #include <sys/mbuf.h>
 #include <sys/socket.h>
 #include <sys/socketvar.h>