diff --git a/lhotse/dataset/unsupervised.py b/lhotse/dataset/unsupervised.py
index e3d91239e..8fd046dcf 100644
--- a/lhotse/dataset/unsupervised.py
+++ b/lhotse/dataset/unsupervised.py
@@ -65,6 +65,8 @@ def __init__(self, collate: bool = True) -> None:
         self.collate = collate
 
     def __getitem__(self, cuts: CutSet) -> Dict[str, Any]:
+        self._validate(cuts)
+
         if self.collate:
             audio, audio_lens = collate_audio(cuts)
             return {