diff --git a/sys/boot/userboot/userboot/conf.c b/sys/boot/userboot/userboot/conf.c
index 0c57eba4d25..2a98434ec23 100644
--- a/sys/boot/userboot/userboot/conf.c
+++ b/sys/boot/userboot/userboot/conf.c
@@ -57,6 +57,7 @@ struct devsw *devsw[] = {
 struct fs_ops *file_system[] = {
 	&host_fsops,
 	&ufs_fsops,
+	&cd9660_fsops,
 	&gzipfs_fsops,
 	NULL
 };
diff --git a/sys/boot/userboot/userboot/main.c b/sys/boot/userboot/userboot/main.c
index 4092b9b6e8b..b9b133720e7 100644
--- a/sys/boot/userboot/userboot/main.c
+++ b/sys/boot/userboot/userboot/main.c
@@ -153,11 +153,13 @@ extract_currdev(void)
 		dev.d_slice = 0;
 		dev.d_partition = 0;
 		/*
-		 * Figure out if we are using MBR or GPT - for GPT we
-		 * set the partition to 0 since everything is a GPT slice.
+		 * If we cannot auto-detect the partition type then
+		 * access the disk as a raw device.
 		 */
-		if (dev.d_dev->dv_open(NULL, &dev))
-			dev.d_partition = 255;
+		if (dev.d_dev->dv_open(NULL, &dev)) {
+			dev.d_slice = -1;
+			dev.d_partition = -1;
+		}
 	} else {
 		dev.d_dev = &host_dev;
 		dev.d_type = dev.d_dev->dv_type;