diff --git a/pfhedge/stochastic/heston.py b/pfhedge/stochastic/heston.py
index 639a716b..fcb00056 100644
--- a/pfhedge/stochastic/heston.py
+++ b/pfhedge/stochastic/heston.py
@@ -92,10 +92,10 @@ def generate_heston(
         dtype=dtype,
         device=device,
     )
-    log_spot = torch.empty(n_paths, n_steps)
-    log_spot[:, 0] = torch.tensor(init_spot).log()
 
-    randn = torch.randn(n_paths, n_steps)
+    log_spot = torch.empty_like(variance)
+    log_spot[:, 0] = torch.tensor(init_spot).log()
+    randn = torch.randn_like(variance)
 
     for i_step in range(n_steps - 1):
         # Compute log S(t + 1): Eq(33)
diff --git a/pyproject.toml b/pyproject.toml
index 87607bb6..4dc79937 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "pfhedge"
-version = "0.7.0"
+version = "0.7.1"
 description = "Deep Hedging in PyTorch"
 authors = ["Shota Imaki <shota.imaki.0801@gmail.com>"]
 license = "MIT"