diff --git a/flake.nix b/flake.nix
index cef84f7..e6590f5 100644
--- a/flake.nix
+++ b/flake.nix
@@ -132,5 +132,11 @@
         echo " UBOOT_ENV = $UBOOT_ENV"
       '';
     };
+
+    devShells.x86_64-linux.lagarto-ox-rd =
+      self.outputs.devShells.x86_64-linux.lagarto-ox.overrideAttrs (old:{
+        TOPLEVEL = "";
+        ROOTFS = "";
+      });
   };
 }
diff --git a/fpga/upload.sh b/fpga/upload.sh
index d64bfa7..783b0ef 100755
--- a/fpga/upload.sh
+++ b/fpga/upload.sh
@@ -16,7 +16,11 @@ rsync -a fpga/env.sh "$dst"
 rsync $OPENSBI/share/opensbi/*/fpga/*/firmware/fw_payload.bin "$dst/opensbi.bin"
 rsync "$KERNEL/Image" "$dst/kernel.bin"
 rsync "$INITRD/initrd" "$dst/initrd.bin"
-rsync "$ROOTFS/sd-image/rootfs.img" "$dst/rootfs.img"
+if [ -n "$ROOTFS" ]; then
+  rsync "$ROOTFS/sd-image/rootfs.img" "$dst/rootfs.img"
+else
+  echo "Skipping rootfs"
+fi
 rsync "$UBOOT_ENV" "$dst/uboot.env"
 
 echo "Now go to $dst and run ./boot.sh"