diff --git a/nac3core/irrt/irrt/ndarray.hpp b/nac3core/irrt/irrt/ndarray.hpp
index 9d305aa4..72ca0b9e 100644
--- a/nac3core/irrt/irrt/ndarray.hpp
+++ b/nac3core/irrt/irrt/ndarray.hpp
@@ -148,4 +148,4 @@ void __nac3_ndarray_calc_broadcast_idx64(const uint64_t* src_dims,
                                          NDIndexInt* out_idx) {
     __nac3_ndarray_calc_broadcast_idx_impl(src_dims, src_ndims, in_idx, out_idx);
 }
-}  // namespace
\ No newline at end of file
+}
\ No newline at end of file
diff --git a/nac3core/irrt/irrt/ndarray/basic.hpp b/nac3core/irrt/irrt/ndarray/basic.hpp
index 05ee30fc..62c92ae2 100644
--- a/nac3core/irrt/irrt/ndarray/basic.hpp
+++ b/nac3core/irrt/irrt/ndarray/basic.hpp
@@ -6,8 +6,7 @@
 #include "irrt/ndarray/def.hpp"
 
 namespace {
-namespace ndarray {
-namespace basic {
+namespace ndarray::basic {
 /**
  * @brief Assert that `shape` does not contain negative dimensions.
  *
@@ -247,8 +246,7 @@ void copy_data(const NDArray<SizeT>* src_ndarray, NDArray<SizeT>* dst_ndarray) {
         ndarray::basic::set_pelement_value(dst_ndarray, dst_element, src_element);
     }
 }
-}  // namespace basic
-}  // namespace ndarray
+}  // namespace ndarray::basic
 }  // namespace
 
 extern "C" {
diff --git a/nac3core/irrt/irrt/ndarray/indexing.hpp b/nac3core/irrt/irrt/ndarray/indexing.hpp
index 9e9e7b6e..76e78473 100644
--- a/nac3core/irrt/irrt/ndarray/indexing.hpp
+++ b/nac3core/irrt/irrt/ndarray/indexing.hpp
@@ -65,8 +65,7 @@ struct NDIndex {
 }  // namespace
 
 namespace {
-namespace ndarray {
-namespace indexing {
+namespace ndarray::indexing {
 /**
  * @brief Perform ndarray "basic indexing" (https://numpy.org/doc/stable/user/basics.indexing.html#basic-indexing)
  *
@@ -162,7 +161,8 @@ void index(SizeT num_indices, const NDIndex* indices, const NDArray<SizeT>* src_
 
             Range<int32_t> range = slice->indices_checked<SizeT>(src_ndarray->shape[src_axis]);
 
-            dst_ndarray->data = static_cast<uint8_t*>(dst_ndarray->data) + (SizeT)range.start * src_ndarray->strides[src_axis];
+            dst_ndarray->data =
+                static_cast<uint8_t*>(dst_ndarray->data) + (SizeT)range.start * src_ndarray->strides[src_axis];
             dst_ndarray->strides[dst_axis] = ((SizeT)range.step) * src_ndarray->strides[src_axis];
             dst_ndarray->shape[dst_axis] = (SizeT)range.len<SizeT>();
 
@@ -197,8 +197,7 @@ void index(SizeT num_indices, const NDIndex* indices, const NDArray<SizeT>* src_
     debug_assert_eq(SizeT, src_ndarray->ndims, src_axis);
     debug_assert_eq(SizeT, dst_ndarray->ndims, dst_axis);
 }
-}  // namespace indexing
-}  // namespace ndarray
+}  // namespace ndarray::indexing
 }  // namespace
 
 extern "C" {