diff --git a/model/pytorch/dcrnn_supervisor.py b/model/pytorch/dcrnn_supervisor.py
index af5732d..c09052e 100644
--- a/model/pytorch/dcrnn_supervisor.py
+++ b/model/pytorch/dcrnn_supervisor.py
@@ -118,7 +118,7 @@ class DCRNNSupervisor:
                 output = self.dcrnn_model(x)
 
                 # (horizon, batch_size, num_sensor * output_dim)
-                for t in y.size(0):
+                for t in range(y.size(0)):
                     per_timestep_loss[t] += self._compute_loss(y[t], output[t])
 
                 num_batches += 1