diff --git a/torch_geometric/nn/conv/han_conv.py b/torch_geometric/nn/conv/han_conv.py
index e1e0128c7443..d406147e89f2 100644
--- a/torch_geometric/nn/conv/han_conv.py
+++ b/torch_geometric/nn/conv/han_conv.py
@@ -23,7 +23,7 @@ def group(
         num_edge_types = len(xs)
         out = torch.stack(xs)
         if out.numel() == 0:
-            return out.view(0, out.size(-1))
+            return out.view(0, out.size(-1)), None
         attn_score = (q * torch.tanh(k_lin(out)).mean(1)).sum(-1)
         attn = F.softmax(attn_score, dim=0)
         out = torch.sum(attn.view(num_edge_types, 1, -1) * out, dim=0)