diff --git a/xnat_ingest/utils.py b/xnat_ingest/utils.py
index 8179feb..e92f2cd 100644
--- a/xnat_ingest/utils.py
+++ b/xnat_ingest/utils.py
@@ -38,6 +38,8 @@ def __init__(
     def convert(
         self, value: ty.Any, param: click.Parameter | None, ctx: click.Context | None
     ):
+        if isinstance(value, self.type):
+            return value
         return self.type(*value)
 
     @property