diff --git a/include/cista/containers/nvec.h b/include/cista/containers/nvec.h
index 7a8ff266..9db6adb4 100644
--- a/include/cista/containers/nvec.h
+++ b/include/cista/containers/nvec.h
@@ -152,7 +152,7 @@ struct basic_nvec {
     using reference = std::add_lvalue_reference<value_type>;
 
     const_bucket(basic_nvec const* map, index_value_type const i)
-        : map_{map}, i_{to_idx(i)} {}
+        : i_{to_idx(i)}, map_{map} {}
 
     template <typename T = std::decay_t<data_value_type>,
               typename = std::enable_if_t<std::is_same_v<T, char>>>
@@ -236,13 +236,13 @@ struct basic_nvec {
   private:
     std::size_t bucket_begin_idx() const { return to_idx(map_->index_[0][i_]); }
     std::size_t bucket_end_idx() const {
-      return to_idx(map_->index_[0][i_ + 1]);
+      return to_idx(map_->index_[0][i_ + 1U]);
     }
     bool is_inside_bucket(std::size_t const i) const {
       return bucket_begin_idx() + i < bucket_end_idx();
     }
 
-    std::size_t i_;
+    size_type i_;
     basic_nvec const* map_;
   };
 
@@ -254,6 +254,11 @@ struct basic_nvec {
 
   template <typename Container>
   void emplace_back(Container&& bucket) {
+    if (index_[0].size() == 0U) {
+      for (auto& i : index_) {
+        i.push_back(0U);
+      }
+    }
     add<N - 1>(bucket);
   }
 
@@ -275,7 +280,7 @@ struct basic_nvec {
     constexpr auto const I = sizeof...(Indices);
     static_assert(I == N - 1);
     verify(to_idx(first) < index_[I].size(), "nvec::at: index out of range");
-    return get_bucket<bucket>(index_[I][first], rest...);
+    return get_bucket(index_[I][first], rest...);
   }
 
   template <typename... Indices>
@@ -283,23 +288,33 @@ struct basic_nvec {
     constexpr auto const I = sizeof...(Indices);
     static_assert(I == N - 1);
     verify(to_idx(first) < index_[I].size(), "nvec::at: index out of range");
-    return get_bucket<const_bucket, Indices...>(index_[I][first], rest...);
+    return get_bucket(index_[I][first], rest...);
   }
 
   auto cista_members() noexcept { return std::tie(index_, data_); }
 
-protected:
-  template <typename BucketType, typename... Rest>
-  BucketType get_bucket(index_value_type const bucket_start,
-                        index_value_type const i, Rest... rest) {
-    return get_bucket<BucketType, Rest...>(
-        index_[sizeof...(Rest)][bucket_start + i], rest...);
+  template <typename... Rest>
+  bucket get_bucket(index_value_type const bucket_start,
+                    index_value_type const i, Rest... rest) {
+    return get_bucket<Rest...>(index_[sizeof...(Rest)][bucket_start + i],
+                               rest...);
+  }
+
+  bucket get_bucket(index_value_type const bucket_start,
+                    index_value_type const i) {
+    return bucket{this, bucket_start + i};
+  }
+
+  template <typename... Rest>
+  const_bucket get_bucket(index_value_type const bucket_start,
+                          index_value_type const i, Rest... rest) const {
+    return get_bucket<Rest...>(index_[sizeof...(Rest)][bucket_start + i],
+                               rest...);
   }
 
-  template <typename BucketType>
-  BucketType get_bucket(index_value_type const bucket_start,
-                        index_value_type const i) {
-    return BucketType{this, bucket_start + i};
+  const_bucket get_bucket(index_value_type const bucket_start,
+                          index_value_type const i) const {
+    return const_bucket{this, bucket_start + i};
   }
 
   template <std::size_t L, typename Container>
diff --git a/include/cista/reflection/to_tuple.h b/include/cista/reflection/to_tuple.h
index 1ac88255..78f7ed3e 100644
--- a/include/cista/reflection/to_tuple.h
+++ b/include/cista/reflection/to_tuple.h
@@ -50,11 +50,12 @@ auto to_ptrs(T&& t) {
 
 template <typename T>
 inline constexpr auto to_tuple_works_v =
-    detail::has_cista_members_v<T> || (std::is_aggregate_v<T> &&
+    detail::has_cista_members_v<T> ||
+    (std::is_aggregate_v<T> &&
 #if !defined(_MSC_VER) || defined(NDEBUG)
-                                       std::is_standard_layout_v<T> &&
+     std::is_standard_layout_v<T> &&
 #endif
-                                       !std::is_polymorphic_v<T>);
+     !std::is_polymorphic_v<T> && !std::is_union_v<T>);
 
 template <typename T,
           std::enable_if_t<detail::has_cista_members_v<T> && std::is_const_v<T>,
diff --git a/include/cista/serialization.h b/include/cista/serialization.h
index ad99e641..290b5c51 100755
--- a/include/cista/serialization.h
+++ b/include/cista/serialization.h
@@ -683,7 +683,7 @@ void recurse(Ctx& c, T* el, Fn&& fn) {
   using Type = decay_t<T>;
   if constexpr (is_indexed_v<Type>) {
     fn(static_cast<typename T::value_type*>(el));
-  } else if constexpr (std::is_aggregate_v<Type> && !std::is_union_v<Type>) {
+  } else if constexpr (to_tuple_works_v<Type>) {
     for_each_ptr_field(*el, [&](auto& f) { fn(f); });
   } else if constexpr (is_mode_enabled(Ctx::MODE, mode::_PHASE_II) &&
                        std::is_pointer_v<Type>) {
diff --git a/test/nvec_test.cc b/test/nvec_test.cc
index 77e95abb..e89718cd 100644
--- a/test/nvec_test.cc
+++ b/test/nvec_test.cc
@@ -7,24 +7,38 @@
 #include "cista.h"
 #else
 #include "cista/containers/nvec.h"
+#include "cista/serialization.h"
+#include "cista/targets/buf.h"
 #endif
 
 TEST_CASE("nvec test") {
+  constexpr auto const kMode =
+      cista::mode::WITH_INTEGRITY | cista::mode::WITH_VERSION;
+
   struct transfer {
     bool operator==(transfer const& o) const { return o.i_ == i_; }
     int i_;
   };
-  cista::raw::nvec<std::uint32_t, transfer, 2> v;
-  v.emplace_back(std::vector<std::vector<transfer>>{
-      {transfer{1}, transfer{2}}, {transfer{3}, transfer{4}, transfer{5}}});
-  v.emplace_back(std::vector<std::vector<transfer>>{
-      {transfer{6}, transfer{7}},
-      {transfer{8}, transfer{9}, transfer{10}},
-      {transfer{11}}});
-  v.emplace_back(std::vector<std::vector<transfer>>{
-      {transfer{12}, transfer{13}},
-      {transfer{14}, transfer{15}, transfer{16}},
-      {transfer{17}}});
+
+  cista::byte_buf buf;
+  {
+    cista::offset::nvec<std::uint32_t, transfer, 2> v;
+    v.emplace_back(std::vector<std::vector<transfer>>{
+        {transfer{1}, transfer{2}}, {transfer{3}, transfer{4}, transfer{5}}});
+    v.emplace_back(std::vector<std::vector<transfer>>{
+        {transfer{6}, transfer{7}},
+        {transfer{8}, transfer{9}, transfer{10}},
+        {transfer{11}}});
+    v.emplace_back(std::vector<std::vector<transfer>>{
+        {transfer{12}, transfer{13}},
+        {transfer{14}, transfer{15}, transfer{16}},
+        {transfer{17}}});
+    buf = cista::serialize<kMode>(v);
+  }
+
+  auto const& v =
+      *cista::deserialize<cista::raw::nvec<std::uint32_t, transfer, 2>, kMode>(
+          buf);
 
   auto const all = std::vector<transfer>{
       transfer{1},  transfer{2},  transfer{3},  transfer{4},  transfer{5},
diff --git a/test/union_derive_test.cc b/test/union_derive_test.cc
index 450403d8..8c669cac 100644
--- a/test/union_derive_test.cc
+++ b/test/union_derive_test.cc
@@ -15,6 +15,7 @@ TEST_CASE("union_test") {
     int32_t a_;
     float b_;
   };
+  static_assert(!cista::to_tuple_works_v<union_type>);
 
   cista::byte_buf buf;