diff --git a/src/datachain/lib/dc.py b/src/datachain/lib/dc.py
index 0e61c35ba..1b05f0364 100644
--- a/src/datachain/lib/dc.py
+++ b/src/datachain/lib/dc.py
@@ -535,7 +535,7 @@ def _udf_to_obj(
         name = self.name or ""
 
         sign = UdfSignature.parse(name, signal_map, func, params, output, is_generator)
-        DataModel.register(sign.output_schema.values.values())
+        DataModel.register(list(sign.output_schema.values.values()))
 
         params_schema = self.signals_schema.slice(sign.params, self._setup)