diff --git a/dn3/data/dataset.py b/dn3/data/dataset.py
index 2a397b6..e5c7dd8 100644
--- a/dn3/data/dataset.py
+++ b/dn3/data/dataset.py
@@ -381,7 +381,7 @@ def __init__(self, epochs: mne.Epochs, session_id=0, person_id=0, force_label=No
             self.epoch_codes_to_class_labels = event_mapping
         else:
             reverse_mapping = {v: k for k, v in event_mapping.items()}
-            self.epoch_codes_to_class_labels = {v: i for i, v in enumerate(sorted(reverse_mapping.keys()))}
+            self.epoch_codes_to_class_labels = {v: i for i, v in enumerate(sorted(reverse_mapping.values()))}
         skip_epochs = list() if skip_epochs is None else skip_epochs
         self._skip_map = [i for i in range(len(self.epochs.events)) if i not in skip_epochs]
         self._skip_map = dict(zip(range(len(self._skip_map)), self._skip_map))