diff --git a/weldx/util/media_file.py b/weldx/util/media_file.py
index 339eb9e62..cba0e0436 100644
--- a/weldx/util/media_file.py
+++ b/weldx/util/media_file.py
@@ -2,7 +2,7 @@
 from __future__ import annotations
 
 from pathlib import Path
-from typing import Union, get_args, get_type_hints
+from typing import Union, get_args
 
 import numpy as np
 import pandas as pd
@@ -136,8 +136,7 @@ def _init_from_sequence(
             resolution=(image.width, image.height),
             nframes=len(path_or_array),
         )
-        _ref_time_types = get_type_hints(MediaFile.__init__)["reference_time"]
-        if not isinstance(reference_time, get_args(_ref_time_types)):
+        if reference_time is not None and not isinstance(reference_time, pd.Timestamp):
             raise ValueError(
                 f"unsupported type for reference_time {type(reference_time)}"
             )