diff --git a/sys/fs/nfsclient/nfs_clbio.c b/sys/fs/nfsclient/nfs_clbio.c
index c3339617acce..06b51c050d34 100644
--- a/sys/fs/nfsclient/nfs_clbio.c
+++ b/sys/fs/nfsclient/nfs_clbio.c
@@ -1001,12 +1001,24 @@ ncl_write(struct vop_write_args *ap)
 	if (uio->uio_resid == 0)
 		return (0);
 
+	/*
+	 * If the file in not mmap()'d, do IO_APPEND writing via a
+	 * synchronous direct write.  This can result in a significant
+	 * performance improvement.
+	 * If the file is mmap()'d, this cannot be done, since there
+	 * is no way to maintain consistency between the file on the
+	 * NFS server and the file's mmap()'d pages.
+	 */
+	NFSLOCKNODE(np);
 	if (vp->v_type == VREG && ((newnfs_directio_enable && (ioflag &
-	    IO_DIRECT)) || (ioflag & IO_APPEND))) {
+	    IO_DIRECT)) || ((ioflag & IO_APPEND) &&
+	    (vp->v_object == NULL || !vm_object_is_active(vp->v_object))))) {
+		NFSUNLOCKNODE(np);
 		if ((ioflag & IO_APPEND) != 0)
 			ioflag |= IO_SYNC;
 		return nfs_directio_write(vp, uio, cred, ioflag);
 	}
+	NFSUNLOCKNODE(np);
 
 	/*
 	 * Maybe this should be above the vnode op call, but so long as