diff --git a/perception/autoware_tensorrt_yolox/include/autoware/tensorrt_yolox/preprocess.hpp b/perception/autoware_tensorrt_yolox/include/autoware/tensorrt_yolox/preprocess.hpp
index 947d6cc6ecc95..7971fbd815deb 100644
--- a/perception/autoware_tensorrt_yolox/include/autoware/tensorrt_yolox/preprocess.hpp
+++ b/perception/autoware_tensorrt_yolox/include/autoware/tensorrt_yolox/preprocess.hpp
@@ -21,7 +21,9 @@
 #include <cuda_runtime_api.h>
 #include <curand.h>
 
-namespace autoware::tensorrt_yolox
+namespace autoware
+{
+namespace tensorrt_yolox
 {
 struct Roi
 {
@@ -195,5 +197,6 @@ extern void multi_scale_resize_bilinear_letterbox_nhwc_to_nchw32_batch_gpu(
 extern void argmax_gpu(
   unsigned char * dst, float * src, int d_w, int d_h, int s_w, int s_h, int s_c, int batch,
   cudaStream_t stream);
-}  // namespace autoware::tensorrt_yolox
+}  // namespace tensorrt_yolox
+}  // namespace autoware
 #endif  // AUTOWARE__TENSORRT_YOLOX__PREPROCESS_HPP_
diff --git a/perception/autoware_tensorrt_yolox/src/preprocess.cu b/perception/autoware_tensorrt_yolox/src/preprocess.cu
index ba9d456f32749..6e8ded20df709 100644
--- a/perception/autoware_tensorrt_yolox/src/preprocess.cu
+++ b/perception/autoware_tensorrt_yolox/src/preprocess.cu
@@ -21,7 +21,9 @@
 
 #define MIN(x, y) x < y ? x : y
 
-namespace autoware::tensorrt_yolox
+namespace autoware
+{
+namespace tensorrt_yolox
 {
 constexpr size_t block = 512;
 
@@ -629,4 +631,5 @@ void argmax_gpu(
     N, dst, src, d_h, d_w, s_c, s_h, s_w, batch);
 }
 
-}  // namespace autoware::tensorrt_yolox
+}  // namespace tensorrt_yolox
+}  // namespace autoware