diff --git a/pfrl/functions/bound_by_tanh.py b/pfrl/functions/bound_by_tanh.py
index 0218f1d26..2b9f656ac 100644
--- a/pfrl/functions/bound_by_tanh.py
+++ b/pfrl/functions/bound_by_tanh.py
@@ -20,4 +20,4 @@ def bound_by_tanh(x, low, high):
     high = torch.as_tensor(high, dtype=x.dtype, device=x.device)
     scale = (high - low) / 2
     loc = (high + low) / 2
-    return nn.functional.tanh(x) * scale + loc
+    return torch.tanh(x) * scale + loc