diff --git a/torchts/utils/graph.py b/torchts/utils/graph.py
index efb4c160..7aac8338 100644
--- a/torchts/utils/graph.py
+++ b/torchts/utils/graph.py
@@ -30,6 +30,9 @@ def reverse_random_walk(adj_mx):
 
 
 def scaled_laplacian(adj_mx, lambda_max=2, undirected=True):
+    if sp.issparse(adj_mx):
+        adj_mx = adj_mx.todense()
+
     if undirected:
         adj_mx = np.maximum.reduce([adj_mx, adj_mx.T])