diff --git a/tests/icosagon/test_fastconv.py b/tests/icosagon/test_fastconv.py
index 963df9b..8aaf00d 100644
--- a/tests/icosagon/test_fastconv.py
+++ b/tests/icosagon/test_fastconv.py
@@ -15,3 +15,22 @@ def test_sparse_diag_cat_01():
     res = _sparse_diag_cat([ m.to_sparse() for m in matrices ])
     res = res.to_dense()
     assert torch.all(res == ground_truth)
+
+
+def test_sparse_diag_cat_02():
+    x = [ torch.rand(5, 10).round() for _ in range(7) ]
+    a = [ m.to_sparse() for m in x ]
+    a = _sparse_diag_cat(a)
+    b = torch.rand(70, 64)
+    res = torch.sparse.mm(a, b)
+
+    ground_truth = torch.zeros(35, 64)
+    ground_truth[0:5, :] = torch.mm(x[0], b[0:10])
+    ground_truth[5:10, :] = torch.mm(x[1], b[10:20])
+    ground_truth[10:15, :] = torch.mm(x[2], b[20:30])
+    ground_truth[15:20, :] = torch.mm(x[3], b[30:40])
+    ground_truth[20:25, :] = torch.mm(x[4], b[40:50])
+    ground_truth[25:30, :] = torch.mm(x[5], b[50:60])
+    ground_truth[30:35, :] = torch.mm(x[6], b[60:70])
+
+    assert torch.all(res == ground_truth)