diff --git a/include/raspimouse_ros2_examples/camera_line_follower_component.hpp b/include/raspimouse_ros2_examples/camera_line_follower_component.hpp
index a960457..0e7a756 100644
--- a/include/raspimouse_ros2_examples/camera_line_follower_component.hpp
+++ b/include/raspimouse_ros2_examples/camera_line_follower_component.hpp
@@ -59,7 +59,7 @@ class Camera_Follower : public rclcpp_lifecycle::LifecycleNode
   std::string mat_type2encoding(const int mat_type) const;
   void convert_frame_to_message(
     const cv::Mat & frame,
-    sensor_msgs::msg::Image & msg);
+    sensor_msgs::msg::Image & msg) const;
 
   bool detecting_line(const cv::Mat & input_frame, cv::Mat & result_frame);
 
diff --git a/src/camera_line_follower_component.cpp b/src/camera_line_follower_component.cpp
index f429f87..cc7ba99 100644
--- a/src/camera_line_follower_component.cpp
+++ b/src/camera_line_follower_component.cpp
@@ -112,7 +112,7 @@ std::string Camera_Follower::mat_type2encoding(const int mat_type) const
 
 // Ref: https://github.com/ros2/demos/blob/dashing/image_tools/src/cam2image.cpp
 void Camera_Follower::convert_frame_to_message(
-  const cv::Mat & frame, sensor_msgs::msg::Image & msg)
+  const cv::Mat & frame, sensor_msgs::msg::Image & msg) const
 {
   // copy cv information into ros message
   msg.height = frame.rows;