diff --git a/improved_diffusion/gaussian_diffusion.py b/improved_diffusion/gaussian_diffusion.py
index 403d474f3b..ae634cdece 100644
--- a/improved_diffusion/gaussian_diffusion.py
+++ b/improved_diffusion/gaussian_diffusion.py
@@ -38,6 +38,18 @@ def get_named_beta_schedule(schedule_name, num_diffusion_timesteps):
             num_diffusion_timesteps,
             lambda t: math.cos((t + 0.008) / 1.008 * math.pi / 2) ** 2,
         )
+    elif schedule_name == "constant":
+        scale = 1000 / num_diffusion_timesteps
+        beta_end = scale * 0.02
+        return beta_end * np.ones(
+            num_diffusion_timesteps, dtype=np.float64
+        )
+    elif schedule_name == "sigmoid":
+        scale = 1000 / num_diffusion_timesteps
+        beta_start = scale * 0.0001
+        beta_end = scale * 0.02
+        betas = np.linspace(-6, 6, num_diffusion_timesteps)
+        return (1/(np.exp(betas) + 1)) * (beta_end - beta_start) + beta_start
     else:
         raise NotImplementedError(f"unknown beta schedule: {schedule_name}")