diff --git a/torchmdnet/datasets/custom.py b/torchmdnet/datasets/custom.py
index 828f86d98..28ef22c42 100644
--- a/torchmdnet/datasets/custom.py
+++ b/torchmdnet/datasets/custom.py
@@ -76,7 +76,7 @@ def __init__(
         print("Number of files: ", len(self.files["pos"]))
         self.cached = False
         total_data_size = self._initialize_index()
-        print(f"Combined dataset size {len(self.index))}")
+        print(f"Combined dataset size {len(self.index)}")
         # If the dataset is small enough, load it whole into CPU memory
         data_size_limit = preload_memory_limit * 1024 * 1024
         if total_data_size < data_size_limit: