diff --git a/model_server/session.py b/model_server/session.py
index 15ee33f4479107a45edcfacedf1cc5c63fcbe123..58e802c2247a5914c2e3dd4240e7222a4f56e63f 100644
--- a/model_server/session.py
+++ b/model_server/session.py
@@ -36,12 +36,12 @@ class Session(object):
     def get_paths(self):
         return self.paths
 
-    def set_data_directory(self, key: str, path: Path):
+    def set_data_directory(self, key: str, path: str):
         if not key in self.paths.keys():
             raise InvalidPathError(f'No such path {key}')
         if not Path(path).exists():
             raise InvalidPathError(f'Could not find {path}')
-        self.paths[key] = path
+        self.paths[key] = Path(path)
 
     @staticmethod
     def make_paths(root: str = None) -> dict: