diff --git a/src/transformers/hf_argparser.py b/src/transformers/hf_argparser.py
index a5cb5d141c9..4ed55a9dab2 100644
--- a/src/transformers/hf_argparser.py
+++ b/src/transformers/hf_argparser.py
@@ -66,7 +66,7 @@ class HfArgumentParser(ArgumentParser):
         super().__init__(**kwargs)
         if dataclasses.is_dataclass(dataclass_types):
             dataclass_types = [dataclass_types]
-        self.dataclass_types = dataclass_types
+        self.dataclass_types = list(dataclass_types)
         for dtype in self.dataclass_types:
             self._add_dataclass_arguments(dtype)