diff --git a/jupyterlite_xeus/add_on.py b/jupyterlite_xeus/add_on.py
index 1b6b148..3d63a99 100644
--- a/jupyterlite_xeus/add_on.py
+++ b/jupyterlite_xeus/add_on.py
@@ -1,4 +1,5 @@
 """a JupyterLite addon for creating the env for xeus kernels"""
+
 import json
 import os
 from pathlib import Path
@@ -294,6 +295,7 @@ def pack_prefix(self, kernel_dir):
 
             host_path, mount_path = mount.split(":")
             mount_path = Path(mount_path)
+            host_path = Path(host_path)
 
             if not mount_path.is_absolute():
                 raise ValueError(f"mount_path {mount_path} needs to be absolute")