diff --git a/lassonet/cox.py b/lassonet/cox.py
index facc338..562975f 100644
--- a/lassonet/cox.py
+++ b/lassonet/cox.py
@@ -31,7 +31,9 @@ def forward(self, log_h, y):
         events = events[idx]
 
         event_ind = events.nonzero().flatten()
-
+        if event_ind.nelement() == 0:
+            return torch.tensor(0.0)
+        
         # numerator
         log_num = log_h[event_ind].mean()