diff --git a/core/io/signal.py b/core/io/signal.py
index 91907bd5cccc1bedaf9eb9c51faa6ee17e7a322c..05ddb6ae2fb054798277756f85bc7551870f1a29 100644
--- a/core/io/signal.py
+++ b/core/io/signal.py
@@ -14,7 +14,7 @@ class Signal(BridgeH5):
     def __getitem__(self, dataset):
         dset = self._hdf[dataset][()]
         attrs = self._hdf[dataset].attrs
-        first_dataset = dataset.split("/")[1] + "/"
+        first_dataset = dataset.split("/")[0] + "/"
         timepoints = self._hdf[first_dataset].attrs["processed_timepoints"]
 
         if "cell_label" in self._hdf[dataset].attrs: