diff --git a/README.md b/README.md
index 8ce781e..aceaa7b 100644
--- a/README.md
+++ b/README.md
@@ -16,7 +16,7 @@ Just add include path to `include` directory of this project.
 ## Syntax
 
 - `void` functions can be called in almost the same way as python code (remind yourself to append `_a` literal to keyword arguments).
-- For `non-void` functions that return some objects, basically the user will need to capsulate *arguments* in `::util::args_(arg1, arg2, ...) == pybind11:tuple` and *keyword arguments* in `::util::kwargs_("k1"_a = v1, "k2"_a = v2, ...) == pybind11::dict`. The returned value is a corresponding wrapper class. Please refer to the examples below.
+- For `non-void` functions that return some objects, basically the user will need to capsulate *arguments* in `args_(arg1, arg2, ...) == pybind11:tuple` and *keyword arguments* in `kwargs_("k1"_a = v1, "k2"_a = v2, ...) == pybind11::dict`. The returned value is a corresponding wrapper class. Please refer to the examples below.
   - exception: `subplots`, 
   - conversion: Wrapper class of matplotlibcpp17 like [::container::BarContainer](https://github.com/soblin/matplotlibcpp17/blob/master/include/matplotlibcpp17/container.h) needs to be passed to python interpreter using `unwrap()` method in *args* and *kwargs*.
 
diff --git a/gallery/artist_animation/animate_decay.cpp b/gallery/artist_animation/animate_decay.cpp
index 494af09..7d493ad 100644
--- a/gallery/artist_animation/animate_decay.cpp
+++ b/gallery/artist_animation/animate_decay.cpp
@@ -13,7 +13,7 @@
 namespace py = pybind11;
 using namespace py::literals;
 using namespace std;
-using namespace matplotlibcpp17::util;
+using namespace matplotlibcpp17;
 using matplotlibcpp17::animation::ArtistAnimation;
 
 int main() {
diff --git a/gallery/artist_animation/cla_pause.cpp b/gallery/artist_animation/cla_pause.cpp
index 5821fff..89fe56e 100644
--- a/gallery/artist_animation/cla_pause.cpp
+++ b/gallery/artist_animation/cla_pause.cpp
@@ -10,7 +10,7 @@
 namespace py = pybind11;
 using namespace py::literals;
 using namespace std;
-using namespace matplotlibcpp17::util;
+using namespace matplotlibcpp17;
 
 int main() {
   py::scoped_interpreter guard{};
diff --git a/gallery/artist_animation/random_walk.cpp b/gallery/artist_animation/random_walk.cpp
index beb2e42..a9122f6 100644
--- a/gallery/artist_animation/random_walk.cpp
+++ b/gallery/artist_animation/random_walk.cpp
@@ -12,7 +12,7 @@
 namespace py = pybind11;
 using namespace py::literals;
 using namespace std;
-using namespace matplotlibcpp17::util;
+using namespace matplotlibcpp17;
 using matplotlibcpp17::animation::ArtistAnimation;
 
 array<double, 3> init_pos() {
diff --git a/gallery/images_contours_and_fields/quiver_demo.cpp b/gallery/images_contours_and_fields/quiver_demo.cpp
index 46aff24..7a29f96 100644
--- a/gallery/images_contours_and_fields/quiver_demo.cpp
+++ b/gallery/images_contours_and_fields/quiver_demo.cpp
@@ -13,7 +13,7 @@
 namespace py = pybind11;
 using namespace py::literals;
 using namespace std;
-using namespace matplotlibcpp17::util;
+using namespace matplotlibcpp17;
 
 int main1() {
   vector<double> X, Y;
diff --git a/gallery/lines_bars_and_markers/bar_label_demo.cpp b/gallery/lines_bars_and_markers/bar_label_demo.cpp
index c1cafda..37652e2 100644
--- a/gallery/lines_bars_and_markers/bar_label_demo.cpp
+++ b/gallery/lines_bars_and_markers/bar_label_demo.cpp
@@ -16,7 +16,7 @@ using namespace py::literals;
 
 using namespace std;
 
-using namespace matplotlibcpp17::util;
+using namespace matplotlibcpp17;
 
 int main1() {
   vector<int> menMeans = {20, 35, 30, 35, -27};
diff --git a/gallery/lines_bars_and_markers/fill.cpp b/gallery/lines_bars_and_markers/fill.cpp
index 247b6ab..d431d48 100644
--- a/gallery/lines_bars_and_markers/fill.cpp
+++ b/gallery/lines_bars_and_markers/fill.cpp
@@ -13,7 +13,7 @@ namespace py = pybind11;
 using namespace py::literals;
 
 using namespace std;
-using namespace matplotlibcpp17::util;
+using namespace matplotlibcpp17;
 
 int main() {
   const double scale = 10;
diff --git a/gallery/lines_bars_and_markers/fill_between_demo.cpp b/gallery/lines_bars_and_markers/fill_between_demo.cpp
index 3358aa4..13abfa8 100644
--- a/gallery/lines_bars_and_markers/fill_between_demo.cpp
+++ b/gallery/lines_bars_and_markers/fill_between_demo.cpp
@@ -25,7 +25,7 @@ template <typename T> std::vector<T> arange(T start, T end, T h) {
 
 using namespace std;
 
-using namespace matplotlibcpp17::util;
+using namespace matplotlibcpp17;
 
 int main1() {
   auto plt = matplotlibcpp17::pyplot::import();
diff --git a/gallery/lines_bars_and_markers/fill_betweenx_demo.cpp b/gallery/lines_bars_and_markers/fill_betweenx_demo.cpp
index 94b04c4..eb111af 100644
--- a/gallery/lines_bars_and_markers/fill_betweenx_demo.cpp
+++ b/gallery/lines_bars_and_markers/fill_betweenx_demo.cpp
@@ -25,7 +25,7 @@ template <typename T> std::vector<T> arange(T start, T end, T h) {
 
 using namespace std;
 
-using namespace matplotlibcpp17::util;
+using namespace matplotlibcpp17;
 
 int main1() {
   auto plt = matplotlibcpp17::pyplot::import();
diff --git a/gallery/lines_bars_and_markers/scatter_hist.cpp b/gallery/lines_bars_and_markers/scatter_hist.cpp
index 080a308..817a4d8 100644
--- a/gallery/lines_bars_and_markers/scatter_hist.cpp
+++ b/gallery/lines_bars_and_markers/scatter_hist.cpp
@@ -13,7 +13,7 @@
 namespace py = pybind11;
 using namespace py::literals;
 using namespace std;
-using namespace matplotlibcpp17::util;
+using namespace matplotlibcpp17;
 
 template <typename T> std::vector<T> arange(T start, T end, T h) {
   int N = static_cast<int>((end - start) / h);
diff --git a/gallery/lines_bars_and_markers/scatter_with_legend.cpp b/gallery/lines_bars_and_markers/scatter_with_legend.cpp
index 69de898..ec4301b 100644
--- a/gallery/lines_bars_and_markers/scatter_with_legend.cpp
+++ b/gallery/lines_bars_and_markers/scatter_with_legend.cpp
@@ -13,7 +13,7 @@
 namespace py = pybind11;
 using namespace py::literals;
 using namespace std;
-using namespace matplotlibcpp17::util;
+using namespace matplotlibcpp17;
 
 int main1() {
   auto plt = matplotlibcpp17::pyplot::import();
diff --git a/gallery/shapes_and_collections/patch_collection.cpp b/gallery/shapes_and_collections/patch_collection.cpp
index e578b3d..623fd1e 100644
--- a/gallery/shapes_and_collections/patch_collection.cpp
+++ b/gallery/shapes_and_collections/patch_collection.cpp
@@ -14,7 +14,7 @@ namespace py = pybind11;
 using namespace py::literals;
 using namespace std;
 using namespace matplotlibcpp17;
-using namespace matplotlibcpp17::util;
+using namespace matplotlibcpp17;
 
 int main() {
   py::scoped_interpreter guard{};
diff --git a/gallery/shapes_and_collections/patches_circle_rectangle.cpp b/gallery/shapes_and_collections/patches_circle_rectangle.cpp
index 9882c8c..65acdaa 100644
--- a/gallery/shapes_and_collections/patches_circle_rectangle.cpp
+++ b/gallery/shapes_and_collections/patches_circle_rectangle.cpp
@@ -12,7 +12,7 @@
 namespace py = pybind11;
 using namespace py::literals;
 using namespace std;
-using namespace matplotlibcpp17::util;
+using namespace matplotlibcpp17;
 using namespace matplotlibcpp17::patches;
 
 int main() {
diff --git a/gallery/statistics/hist.cpp b/gallery/statistics/hist.cpp
index 4d0cdde..09e45e0 100644
--- a/gallery/statistics/hist.cpp
+++ b/gallery/statistics/hist.cpp
@@ -10,7 +10,7 @@
 namespace py = pybind11;
 using namespace py::literals;
 using namespace std;
-using namespace matplotlibcpp17::util;
+using namespace matplotlibcpp17;
 
 int main1() {
   int N_points = 100000;
diff --git a/gallery/subplots_axes_and_figures/align_labels_demo.cpp b/gallery/subplots_axes_and_figures/align_labels_demo.cpp
index 8196263..cdbf065 100644
--- a/gallery/subplots_axes_and_figures/align_labels_demo.cpp
+++ b/gallery/subplots_axes_and_figures/align_labels_demo.cpp
@@ -27,7 +27,7 @@ template <typename T> std::vector<T> arange(T start, T end, T h) {
 using namespace std;
 
 using matplotlibcpp17::gridspec::GridSpec;
-using namespace matplotlibcpp17::util;
+using namespace matplotlibcpp17;
 
 int main() {
   py::scoped_interpreter guard{};
diff --git a/gallery/subplots_axes_and_figures/gridspec_multicolumn.cpp b/gallery/subplots_axes_and_figures/gridspec_multicolumn.cpp
index 108d3f1..76ce6fd 100644
--- a/gallery/subplots_axes_and_figures/gridspec_multicolumn.cpp
+++ b/gallery/subplots_axes_and_figures/gridspec_multicolumn.cpp
@@ -14,7 +14,7 @@ using namespace py::literals;
 using namespace std;
 
 using matplotlibcpp17::gridspec::GridSpec;
-using namespace matplotlibcpp17::util;
+using namespace matplotlibcpp17;
 
 int main() {
   py::scoped_interpreter guard{};
diff --git a/gallery/subplots_axes_and_figures/multiple_figs_demo.cpp b/gallery/subplots_axes_and_figures/multiple_figs_demo.cpp
index 5b38ff3..b00081a 100644
--- a/gallery/subplots_axes_and_figures/multiple_figs_demo.cpp
+++ b/gallery/subplots_axes_and_figures/multiple_figs_demo.cpp
@@ -25,7 +25,7 @@ template <typename T> std::vector<T> arange(T start, T end, T h) {
 }
 
 using namespace std;
-using namespace matplotlibcpp17::util;
+using namespace matplotlibcpp17;
 
 int main() {
   py::scoped_interpreter guard{};
diff --git a/include/matplotlibcpp17/matplotlibcpp17.h b/include/matplotlibcpp17/matplotlibcpp17.h
index d474ff9..8939ab8 100644
--- a/include/matplotlibcpp17/matplotlibcpp17.h
+++ b/include/matplotlibcpp17/matplotlibcpp17.h
@@ -18,7 +18,12 @@ namespace matplotlibcpp17 {
 #include "figure.h"
 #include "patches.h"
 #include "pyplot.h"
-#include "util.h"
+
+template <typename... Args> pybind11::tuple args_(Args &&... args) {
+  return pybind11::make_tuple(std::forward<Args>(args)...);
+}
+
+using kwargs_ = pybind11::dict;
 
 } // namespace matplotlibcpp17
 
diff --git a/include/matplotlibcpp17/util.h b/include/matplotlibcpp17/util.h
index d679c8b..e69de29 100644
--- a/include/matplotlibcpp17/util.h
+++ b/include/matplotlibcpp17/util.h
@@ -1,9 +0,0 @@
-namespace util {
-
-template <typename... Args> pybind11::tuple args_(Args &&... args) {
-  return pybind11::make_tuple(std::forward<Args>(args)...);
-}
-
-using kwargs_ = pybind11::dict;
-
-} // namespace util