diff --git a/sys/fs/fifofs/fifo_vnops.c b/sys/fs/fifofs/fifo_vnops.c
index fb84263e1dbc..6947c472a64d 100644
--- a/sys/fs/fifofs/fifo_vnops.c
+++ b/sys/fs/fifofs/fifo_vnops.c
@@ -168,6 +168,7 @@ fifo_open(ap)
 		int  a_mode;
 		struct ucred *a_cred;
 		struct thread *a_td;
+		int a_fdidx;
 	} */ *ap;
 {
 	struct vnode *vp = ap->a_vp;