diff --git a/simulator/tier4_dummy_object_rviz_plugin/src/tools/interactive_object.cpp b/simulator/tier4_dummy_object_rviz_plugin/src/tools/interactive_object.cpp
index ca55bc20276e9..bcd56256bde34 100644
--- a/simulator/tier4_dummy_object_rviz_plugin/src/tools/interactive_object.cpp
+++ b/simulator/tier4_dummy_object_rviz_plugin/src/tools/interactive_object.cpp
@@ -221,7 +221,7 @@ boost::optional<tf2::Transform> InteractiveObjectCollection::transform(
   return {};
 }
 
-size_t InteractiveObjectCollection::nearest(const Ogre::Vector3 & point)
+size_t InteractiveObjectCollection::nearest(const Ogre::Vector3 & point) const
 {
   const size_t npos = objects_.size();
   if (objects_.empty()) {
diff --git a/simulator/tier4_dummy_object_rviz_plugin/src/tools/interactive_object.hpp b/simulator/tier4_dummy_object_rviz_plugin/src/tools/interactive_object.hpp
index c1ec65a0488bd..c0942d9a6cdd1 100644
--- a/simulator/tier4_dummy_object_rviz_plugin/src/tools/interactive_object.hpp
+++ b/simulator/tier4_dummy_object_rviz_plugin/src/tools/interactive_object.hpp
@@ -124,7 +124,7 @@ class InteractiveObjectCollection
     const std::array<uint8_t, 16> & uuid) const;
 
 private:
-  size_t nearest(const Ogre::Vector3 & point);
+  size_t nearest(const Ogre::Vector3 & point) const;
   InteractiveObject * target_;
   std::vector<std::unique_ptr<InteractiveObject>> objects_;
 };