diff --git a/evojax/obs_norm.py b/evojax/obs_norm.py
index 0078e0a2..13ca9a6a 100644
--- a/evojax/obs_norm.py
+++ b/evojax/obs_norm.py
@@ -46,6 +46,12 @@ def update_obs_params(obs_buffer: jnp.ndarray,
 
     obs_steps = obs_params[0]
     running_mean, running_var = jnp.split(obs_params[1:], 2)
+
+    # reshape obs_params to support multi-dim observations
+    obs_shape = obs_buffer.shape[2:]  # obs_buffer shape is [n_obs, pop_size, *obs_size]
+    running_mean = running_mean.reshape(obs_shape)
+    running_var = running_var.reshape(obs_shape)
+
     if obs_mask.ndim != obs_buffer.ndim:
         obs_mask = obs_mask.reshape(
             obs_mask.shape + (1,) * (obs_buffer.ndim - obs_mask.ndim))
@@ -61,7 +67,7 @@ def update_obs_params(obs_buffer: jnp.ndarray,
     var_diff = jnp.sum(input_to_new_mean * input_to_old_mean, axis=(0, 1))
     new_var = running_var + var_diff
 
-    return jnp.concatenate([jnp.ones(1) * total_steps, new_mean, new_var])
+    return jnp.concatenate([jnp.ones(1) * total_steps, new_mean.flatten(), new_var.flatten()])
 
 
 class ObsNormalizer(object):