diff --git a/10-Unscented-Kalman-Filter.ipynb b/10-Unscented-Kalman-Filter.ipynb
index 2a1a9e8..c7098b5 100644
--- a/10-Unscented-Kalman-Filter.ipynb
+++ b/10-Unscented-Kalman-Filter.ipynb
@@ -1708,7 +1708,7 @@
    "source": [
     "To include the doppler we need to add the velocity in $x$ and $y$ into the measurement. The `ACSim` class stores the velocity in the data member `vel`. To perform the Kalman filter update we just need to call `update` with a list containing the bearing, distance, and velocity in $x$ and $y$:\n",
     "\n",
-    "$$z = [\\text{slant_range}, \\text{bearing}, \\dot x, \\dot y]$$\n",
+    "$$z = [\\mathtt{slant\\_range}, \\text{bearing}, \\dot x, \\dot y]$$\n",
     "\n",
     "The measurement contains four values so the measurement function also needs to return four values. The slant range and bearing will be computed as before, but we do not need to compute the velocity in $x$ and $y$ as they are provided in the state estimate."
    ]