diff --git a/04-One-Dimensional-Kalman-Filters.ipynb b/04-One-Dimensional-Kalman-Filters.ipynb
index c3c1898..6ab7705 100644
--- a/04-One-Dimensional-Kalman-Filters.ipynb
+++ b/04-One-Dimensional-Kalman-Filters.ipynb
@@ -938,7 +938,7 @@
     "\n",
     "```python\n",
     "prior = predict(x, process_model)\n",
-    "likelihood = likelihood(z, sensor_var)\n",
+    "likelihood = gaussian(z, sensor_var)\n",
     "x = update(prior, likelihood)\n",
     "```\n",
     "\n",