diff --git a/nac3core/irrt/irrt/original.hpp b/nac3core/irrt/irrt/original.hpp
index 97d5ec48..c27cf8a9 100644
--- a/nac3core/irrt/irrt/original.hpp
+++ b/nac3core/irrt/irrt/original.hpp
@@ -4,7 +4,7 @@
 #include <irrt/math_util.hpp>
 
 // NDArray indices are always `uint32_t`.
-using NDIndex = uint32_t;
+using NDIndexInt = uint32_t;
 // The type of an index or a value describing the length of a range/slice is always `int32_t`.
 using SliceIndex = int32_t;
 
@@ -44,7 +44,7 @@ SizeT __nac3_ndarray_calc_size_impl(const SizeT *list_data, SizeT list_len, Size
 }
 
 template <typename SizeT>
-void __nac3_ndarray_calc_nd_indices_impl(SizeT index, const SizeT *dims, SizeT num_dims, NDIndex *idxs)
+void __nac3_ndarray_calc_nd_indices_impl(SizeT index, const SizeT *dims, SizeT num_dims, NDIndexInt *idxs)
 {
     SizeT stride = 1;
     for (SizeT dim = 0; dim < num_dims; dim++)
@@ -57,7 +57,7 @@ void __nac3_ndarray_calc_nd_indices_impl(SizeT index, const SizeT *dims, SizeT n
 }
 
 template <typename SizeT>
-SizeT __nac3_ndarray_flatten_index_impl(const SizeT *dims, SizeT num_dims, const NDIndex *indices, SizeT num_indices)
+SizeT __nac3_ndarray_flatten_index_impl(const SizeT *dims, SizeT num_dims, const NDIndexInt *indices, SizeT num_indices)
 {
     SizeT idx = 0;
     SizeT stride = 1;
@@ -115,8 +115,8 @@ void __nac3_ndarray_calc_broadcast_impl(const SizeT *lhs_dims, SizeT lhs_ndims,
 }
 
 template <typename SizeT>
-void __nac3_ndarray_calc_broadcast_idx_impl(const SizeT *src_dims, SizeT src_ndims, const NDIndex *in_idx,
-                                            NDIndex *out_idx)
+void __nac3_ndarray_calc_broadcast_idx_impl(const SizeT *src_dims, SizeT src_ndims, const NDIndexInt *in_idx,
+                                            NDIndexInt *out_idx)
 {
     for (SizeT i = 0; i < src_ndims; ++i)
     {
@@ -324,23 +324,23 @@ extern "C"
         return __nac3_ndarray_calc_size_impl(list_data, list_len, begin_idx, end_idx);
     }
 
-    void __nac3_ndarray_calc_nd_indices(uint32_t index, const uint32_t *dims, uint32_t num_dims, NDIndex *idxs)
+    void __nac3_ndarray_calc_nd_indices(uint32_t index, const uint32_t *dims, uint32_t num_dims, NDIndexInt *idxs)
     {
         __nac3_ndarray_calc_nd_indices_impl(index, dims, num_dims, idxs);
     }
 
-    void __nac3_ndarray_calc_nd_indices64(uint64_t index, const uint64_t *dims, uint64_t num_dims, NDIndex *idxs)
+    void __nac3_ndarray_calc_nd_indices64(uint64_t index, const uint64_t *dims, uint64_t num_dims, NDIndexInt *idxs)
     {
         __nac3_ndarray_calc_nd_indices_impl(index, dims, num_dims, idxs);
     }
 
-    uint32_t __nac3_ndarray_flatten_index(const uint32_t *dims, uint32_t num_dims, const NDIndex *indices,
+    uint32_t __nac3_ndarray_flatten_index(const uint32_t *dims, uint32_t num_dims, const NDIndexInt *indices,
                                           uint32_t num_indices)
     {
         return __nac3_ndarray_flatten_index_impl(dims, num_dims, indices, num_indices);
     }
 
-    uint64_t __nac3_ndarray_flatten_index64(const uint64_t *dims, uint64_t num_dims, const NDIndex *indices,
+    uint64_t __nac3_ndarray_flatten_index64(const uint64_t *dims, uint64_t num_dims, const NDIndexInt *indices,
                                             uint64_t num_indices)
     {
         return __nac3_ndarray_flatten_index_impl(dims, num_dims, indices, num_indices);
@@ -358,14 +358,14 @@ extern "C"
         return __nac3_ndarray_calc_broadcast_impl(lhs_dims, lhs_ndims, rhs_dims, rhs_ndims, out_dims);
     }
 
-    void __nac3_ndarray_calc_broadcast_idx(const uint32_t *src_dims, uint32_t src_ndims, const NDIndex *in_idx,
-                                           NDIndex *out_idx)
+    void __nac3_ndarray_calc_broadcast_idx(const uint32_t *src_dims, uint32_t src_ndims, const NDIndexInt *in_idx,
+                                           NDIndexInt *out_idx)
     {
         __nac3_ndarray_calc_broadcast_idx_impl(src_dims, src_ndims, in_idx, out_idx);
     }
 
-    void __nac3_ndarray_calc_broadcast_idx64(const uint64_t *src_dims, uint64_t src_ndims, const NDIndex *in_idx,
-                                             NDIndex *out_idx)
+    void __nac3_ndarray_calc_broadcast_idx64(const uint64_t *src_dims, uint64_t src_ndims, const NDIndexInt *in_idx,
+                                             NDIndexInt *out_idx)
     {
         __nac3_ndarray_calc_broadcast_idx_impl(src_dims, src_ndims, in_idx, out_idx);
     }