diff --git a/perception/radar_fusion_to_detected_object/include/radar_fusion_to_detected_object.hpp b/perception/radar_fusion_to_detected_object/include/radar_fusion_to_detected_object.hpp
index b81ca1e7700ad..0d39c4534e54c 100644
--- a/perception/radar_fusion_to_detected_object/include/radar_fusion_to_detected_object.hpp
+++ b/perception/radar_fusion_to_detected_object/include/radar_fusion_to_detected_object.hpp
@@ -42,6 +42,45 @@ using geometry_msgs::msg::TwistWithCovariance;
 using tier4_autoware_utils::LinearRing2d;
 using tier4_autoware_utils::Point2d;
 
+enum MSG_COV_IDX {
+  X_X = 0,
+  X_Y = 1,
+  X_Z = 2,
+  X_ROLL = 3,
+  X_PITCH = 4,
+  X_YAW = 5,
+  Y_X = 6,
+  Y_Y = 7,
+  Y_Z = 8,
+  Y_ROLL = 9,
+  Y_PITCH = 10,
+  Y_YAW = 11,
+  Z_X = 12,
+  Z_Y = 13,
+  Z_Z = 14,
+  Z_ROLL = 15,
+  Z_PITCH = 16,
+  Z_YAW = 17,
+  ROLL_X = 18,
+  ROLL_Y = 19,
+  ROLL_Z = 20,
+  ROLL_ROLL = 21,
+  ROLL_PITCH = 22,
+  ROLL_YAW = 23,
+  PITCH_X = 24,
+  PITCH_Y = 25,
+  PITCH_Z = 26,
+  PITCH_ROLL = 27,
+  PITCH_PITCH = 28,
+  PITCH_YAW = 29,
+  YAW_X = 30,
+  YAW_Y = 31,
+  YAW_Z = 32,
+  YAW_ROLL = 33,
+  YAW_PITCH = 34,
+  YAW_YAW = 35
+};
+
 class RadarFusionToDetectedObject
 {
 public:
diff --git a/perception/radar_fusion_to_detected_object/src/radar_fusion_to_detected_object.cpp b/perception/radar_fusion_to_detected_object/src/radar_fusion_to_detected_object.cpp
index 834a764fe75e2..144166f500702 100644
--- a/perception/radar_fusion_to_detected_object/src/radar_fusion_to_detected_object.cpp
+++ b/perception/radar_fusion_to_detected_object/src/radar_fusion_to_detected_object.cpp
@@ -129,7 +129,7 @@ bool RadarFusionToDetectedObject::hasTwistCovariance(
   const TwistWithCovariance & twist_with_covariance)
 {
   auto covariance = twist_with_covariance.covariance;
-  if (covariance.at(0) == 0.0 && covariance.at(7) == 0.0 && covariance.at(14) == 0.0) {
+  if (covariance[X_X] == 0.0 && covariance[Y_Y] == 0.0 && covariance[Z_Z] == 0.0) {
     return false;
   } else {
     return true;