diff --git a/perception/traffic_light_fine_detector/src/nodelet.cpp b/perception/traffic_light_fine_detector/src/nodelet.cpp
index 8037dc5472fbe..e06ffcad66d21 100644
--- a/perception/traffic_light_fine_detector/src/nodelet.cpp
+++ b/perception/traffic_light_fine_detector/src/nodelet.cpp
@@ -32,12 +32,14 @@ namespace
 float calWeightedIou(
   const sensor_msgs::msg::RegionOfInterest & bbox1, const tensorrt_yolox::Object & bbox2)
 {
-  int x1 = std::max(static_cast<int>(bbox1.x_offset), bbox2.x_offset);
-  int x2 = std::min(static_cast<int>(bbox1.x_offset + bbox1.width), bbox2.x_offset + bbox2.width);
-  int y1 = std::max(static_cast<int>(bbox1.y_offset), bbox2.y_offset);
-  int y2 = std::min(static_cast<int>(bbox1.y_offset + bbox1.height), bbox2.y_offset + bbox2.height);
-  int area1 = std::max(x2 - x1, 0) * std::max(y2 - y1, 0);
-  int area2 = bbox1.width * bbox1.height + bbox2.width * bbox2.height - area1;
+  const int x1 = std::max(static_cast<int>(bbox1.x_offset), bbox2.x_offset);
+  const int x2 =
+    std::min(static_cast<int>(bbox1.x_offset + bbox1.width), bbox2.x_offset + bbox2.width);
+  const int y1 = std::max(static_cast<int>(bbox1.y_offset), bbox2.y_offset);
+  const int y2 =
+    std::min(static_cast<int>(bbox1.y_offset + bbox1.height), bbox2.y_offset + bbox2.height);
+  const int area1 = std::max(x2 - x1, 0) * std::max(y2 - y1, 0);
+  const int area2 = bbox1.width * bbox1.height + bbox2.width * bbox2.height - area1;
   if (area2 == 0) {
     return 0.0;
   }