diff --git a/jax_cosmo/scipy/interpolate.py b/jax_cosmo/scipy/interpolate.py
index 40ad80d..585fabc 100644
--- a/jax_cosmo/scipy/interpolate.py
+++ b/jax_cosmo/scipy/interpolate.py
@@ -229,6 +229,7 @@ def __init__(self, x, y, k=3, endpoints="not-a-knot", coefficients=None):
         self._x = x
         self._y = y
         self._coefficients = coefficients
+        self._endpoints = endpoints
 
     # Operations for flattening/unflattening representation
     def tree_flatten(self):