diff --git a/filterpy/kalman/CubatureKalmanFilter.py b/filterpy/kalman/CubatureKalmanFilter.py
index 74018763..d36eb911 100644
--- a/filterpy/kalman/CubatureKalmanFilter.py
+++ b/filterpy/kalman/CubatureKalmanFilter.py
@@ -318,9 +318,9 @@ def predict(self, dt=None, fx_args=()):
 
         # evaluate cubature points
         for k in range(self._num_sigmas):
-            self.sigmas_f[k] = self.fx(sigmas[k], dt, *fx_args)
+            sigmas_f[k] = self.fx(sigmas[k], dt, *fx_args)
 
-        self.x, self.P = ckf_transform(self.sigmas_f, self.Q)
+        self.x, self.P = ckf_transform(sigmas_f, self.Q)
 
         # save prior
         self.x_prior = self.x.copy()
@@ -359,6 +359,8 @@ def update(self, z, R=None, hx_args=()):
         elif isscalar(R):
             R = eye(self.dim_z) * R
 
+        self.sigmas_f = spherical_radial_sigmas(self.x, self.P)
+
         for k in range(self._num_sigmas):
             self.sigmas_h[k] = self.hx(self.sigmas_f[k], *hx_args)