diff --git a/10-Unscented-Kalman-Filter.ipynb b/10-Unscented-Kalman-Filter.ipynb
index 105511d..ecd34e1 100644
--- a/10-Unscented-Kalman-Filter.ipynb
+++ b/10-Unscented-Kalman-Filter.ipynb
@@ -2449,7 +2449,7 @@
     "    # compute cross variance of the state and the measurements\n",
     "    Pxz = np.zeros((self._dim_x, self._dim_z))\n",
     "    for i in range(self._num_sigmas):\n",
-    "        Pxz += self.W[i] * np.outer(sigmas_f[i] - self.xp,\n",
+    "        Pxz += self.Wc[i] * np.outer(sigmas_f[i] - self.xp,\n",
     "                                    sigmas_h[i] - zp)\n",
     "\n",
     "    K = dot(Pxz, inv(Pz)) # Kalman gain\n",