diff --git a/jax_cosmo/core.py b/jax_cosmo/core.py
index 4ff49d6..badf7a3 100644
--- a/jax_cosmo/core.py
+++ b/jax_cosmo/core.py
@@ -120,7 +120,8 @@ def tree_flatten(self):
     def tree_unflatten(cls, aux_data, children):
         # Retrieve base parameters
         Omega_c, Omega_b, h, n_s, sigma8, Omega_k, w0, wa = children[:8]
-        children = list(children[8:]).reverse()
+        children = list(children[8:])
+        children.reverse()
 
         # We extract the remaining parameters in reverse order from how they
         # were inserted