diff --git a/module/zfs/vdev_disk.c b/module/zfs/vdev_disk.c
index d096d754f7..33b7f5d155 100644
--- a/module/zfs/vdev_disk.c
+++ b/module/zfs/vdev_disk.c
@@ -693,8 +693,6 @@ vdev_disk_io_start(zio_t *zio)
 				return;
 
 			zio->io_error = error;
-			if (error == ENOTSUP)
-				v->vdev_nowritecache = B_TRUE;
 
 			break;
 
diff --git a/module/zfs/zio.c b/module/zfs/zio.c
index 577ee76945..0039407953 100644
--- a/module/zfs/zio.c
+++ b/module/zfs/zio.c
@@ -3393,6 +3393,16 @@ zio_vdev_io_assess(zio_t *zio)
 		vd->vdev_cant_write = B_TRUE;
 	}
 
+	/*
+	 * If a cache flush returns ENOTSUP or ENOTTY, we know that no future
+	 * attempts will ever succeed. In this case we set a persistent bit so
+	 * that we don't bother with it in the future.
+	 */
+	if ((zio->io_error == ENOTSUP || zio->io_error == ENOTTY) &&
+	    zio->io_type == ZIO_TYPE_IOCTL &&
+	    zio->io_cmd == DKIOCFLUSHWRITECACHE && vd != NULL)
+		vd->vdev_nowritecache = B_TRUE;
+
 	if (zio->io_error)
 		zio->io_pipeline = ZIO_INTERLOCK_PIPELINE;