diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4348486..9da12aa 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -10,7 +10,7 @@ if(NOT DEFINED ADD_DEMO)
 endif()
 
 if(NOT DEFINED USE_GUI)
-  set(USE_GUI OFF)
+  set(USE_GUI 0)
 endif()
 
 set(matplotlibcpp17_INCLUDE_DIRS "${CMAKE_CURRENT_SOURCE_DIR}/include")
diff --git a/README.md b/README.md
index aceaa7b..71bae66 100644
--- a/README.md
+++ b/README.md
@@ -148,7 +148,9 @@ From [gallery/artist_animation/random_walk.cpp](https://github.com/soblin/matplo
 mkdir build; cd build; cmake .. ; make -j
 ```
 
-If you want to see the demo with `plt.show()`, add `-DUSE_GUI=ON` (by default it is `OFF`). Otherwise the executables will `plt.savefig()` to each source directory. Then `make <gallery directory name>` runs all executables under that directory.
+If you want to see the demo with `plt.show()`, add `-DUSE_GUI=1` (by default it is `0`). Otherwise the executables will `plt.savefig()` to `gallery/images` directory.
+
+`make <gallery directory name>` runs all executables under that directory.
 
 ```bash
 make lines_bars_and_markers
diff --git a/include/matplotlibcpp17/animation.h b/include/matplotlibcpp17/animation.h
index 6f4aaa4..fbd4623 100644
--- a/include/matplotlibcpp17/animation.h
+++ b/include/matplotlibcpp17/animation.h
@@ -1,4 +1,11 @@
-namespace animation {
+#ifndef MATPLOTLIBCPP17_ANIMATION_H
+#define MATPLOTLIBCPP17_ANIMATION_H
+
+#include <pybind11/pybind11.h>
+
+#include <matplotlibcpp17/common.h>
+
+namespace matplotlibcpp17::animation {
 
 struct DECL_STRUCT_ATTR ArtistAnimation {
   ArtistAnimation(const pybind11::tuple &args, const pybind11::dict &kwargs) {
@@ -14,4 +21,6 @@ struct DECL_STRUCT_ATTR ArtistAnimation {
   pybind11::object save;
 };
 
-} // namespace animation
+} // namespace matplotlibcpp17::animation
+
+#endif /* MATPLOTLIBCPP17_ANIMATION_H */
diff --git a/include/matplotlibcpp17/axes.h b/include/matplotlibcpp17/axes.h
index 394e8ef..823fb2c 100644
--- a/include/matplotlibcpp17/axes.h
+++ b/include/matplotlibcpp17/axes.h
@@ -1,4 +1,19 @@
-namespace axes {
+#ifndef MATPLOTLIBCPP17_AXES_H
+#define MATPLOTLIBCPP17_AXES_H
+
+#include <vector>
+#include <tuple>
+
+#include <matplotlibcpp17/common.h>
+#include <matplotlibcpp17/collections.h>
+#include <matplotlibcpp17/container.h>
+#include <matplotlibcpp17/legend.h>
+#include <matplotlibcpp17/quiver.h>
+#include <matplotlibcpp17/text.h>
+
+#include <pybind11/pybind11.h>
+
+namespace matplotlibcpp17::axes {
 
 struct DECL_STRUCT_ATTR Axes {
   Axes(pybind11::object axes) {
@@ -248,4 +263,6 @@ Axes::scatter(const pybind11::tuple &args = pybind11::tuple(),
   return collections::PathCollection(obj);
 }
 
-} // namespace axes
+} // namespace matplotlibcpp17::axes
+
+#endif /* MATPLOTLIBCPP17_AXES_H */
diff --git a/include/matplotlibcpp17/collections.h b/include/matplotlibcpp17/collections.h
index 295af33..6f73ba9 100644
--- a/include/matplotlibcpp17/collections.h
+++ b/include/matplotlibcpp17/collections.h
@@ -1,4 +1,13 @@
-namespace collections {
+#ifndef MATPLOTLIBCPP17_COLLECTIONS_H
+#define MATPLOTLIBCPP17_COLLECTIONS_H
+
+#include <utility>
+
+#include <matplotlibcpp17/common.h>
+
+#include <pybind11/pybind11.h>
+
+namespace matplotlibcpp17::collections {
 
 struct DECL_STRUCT_ATTR PathCollection {
   PathCollection(pybind11::object pathcollection) {
@@ -47,4 +56,6 @@ struct DECL_STRUCT_ATTR PatchCollection {
   pybind11::object set_array;
 };
 
-} // namespace collections
+} // namespace matplotlibcpp17::collections
+
+#endif /* MATPLOTLIBCPP17_COLLECTIONS_H */
diff --git a/include/matplotlibcpp17/common.h b/include/matplotlibcpp17/common.h
index 3c3d785..5d1bb90 100644
--- a/include/matplotlibcpp17/common.h
+++ b/include/matplotlibcpp17/common.h
@@ -1,3 +1,6 @@
+#ifndef MATPLOTLIBCPP17_COMMON_H
+#define MATPLOTLIBCPP17_COMMON_H
+
 #define LOAD_VOID_ATTR(obj, mod)                                               \
   do {                                                                         \
     obj = mod.attr(#obj);                                                      \
@@ -9,3 +12,5 @@
   } while (0)
 
 #define DECL_STRUCT_ATTR __attribute__((visibility("hidden")))
+
+#endif /* MATPLOTLIBCPP17_COMMON_H */
diff --git a/include/matplotlibcpp17/container.h b/include/matplotlibcpp17/container.h
index ef43940..7e109f4 100644
--- a/include/matplotlibcpp17/container.h
+++ b/include/matplotlibcpp17/container.h
@@ -1,4 +1,11 @@
-namespace container {
+#ifndef MATPLOTLIBCPP17_CONTAINER_H
+#define MATPLOTLIBCPP17_CONTAINER_H
+
+#include <matplotlibcpp17/common.h>
+
+#include <pybind11/pybind11.h>
+
+namespace matplotlibcpp17::container {
 
 struct DECL_STRUCT_ATTR BarContainer {
   BarContainer(pybind11::object bar_container) { self = bar_container; }
@@ -9,4 +16,6 @@ struct DECL_STRUCT_ATTR BarContainer {
   pybind11::object unwrap() { return self; }
 };
 
-} // namespace container
+} // namespace matplotlibcpp17::container
+
+#endif /* MATPLOTLIBCPP17_CONTAINER_H */
diff --git a/include/matplotlibcpp17/figure.h b/include/matplotlibcpp17/figure.h
index 505ae3c..7e3cf7c 100644
--- a/include/matplotlibcpp17/figure.h
+++ b/include/matplotlibcpp17/figure.h
@@ -1,4 +1,13 @@
-namespace figure {
+#ifndef MATPLOTLIBCPP17_FIGURE_H
+#define MATPLOTLIBCPP17_FIGURE_H
+
+#include <matplotlibcpp17/common.h>
+#include <matplotlibcpp17/axes.h>
+#include <matplotlibcpp17/gridspec.h>
+
+#include <pybind11/pybind11.h>
+
+namespace matplotlibcpp17::figure {
 
 struct DECL_STRUCT_ATTR Figure {
   Figure(pybind11::object figure) {
@@ -72,4 +81,6 @@ Figure::add_subplot(const pybind11::tuple &args = pybind11::tuple(),
   pybind11::object obj = add_subplot_attr(*args, **kwargs);
   return axes::Axes(obj);
 }
-} // namespace figure
+} // namespace matplotlibcpp17::figure
+
+#endif /* MATPLOTLIBCPP17_FIGURE_H */
diff --git a/include/matplotlibcpp17/gridspec.h b/include/matplotlibcpp17/gridspec.h
index 76f1d2d..f37f953 100644
--- a/include/matplotlibcpp17/gridspec.h
+++ b/include/matplotlibcpp17/gridspec.h
@@ -1,4 +1,11 @@
-namespace gridspec {
+#ifndef MATPLOTLIBCPP17_GRIDSPEC_H
+#define MATPLOTLIBCPP17_GRIDSPEC_H
+
+#include <matplotlibcpp17/common.h>
+
+#include <pybind11/pybind11.h>
+
+namespace matplotlibcpp17::gridspec {
 
 struct DECL_STRUCT_ATTR SubplotSpec {
   SubplotSpec(pybind11::object subplotspec) { self = subplotspec; }
@@ -29,4 +36,6 @@ struct DECL_STRUCT_ATTR GridSpec {
   pybind11::object gridspec_attr;
 };
 
-} // namespace gridspec
+} // namespace matplotlibcpp17::gridspec
+
+#endif /* MATPLOTLIBCPP17_GRIDSPEC_H */
diff --git a/include/matplotlibcpp17/legend.h b/include/matplotlibcpp17/legend.h
index 8eb3f22..e113a10 100644
--- a/include/matplotlibcpp17/legend.h
+++ b/include/matplotlibcpp17/legend.h
@@ -1,4 +1,11 @@
-namespace legend {
+#ifndef MATPLOTLIBCPP17_LEGEND_H
+#define MATPLOTLIBCPP17_LEGEND_H
+
+#include <matplotlibcpp17/common.h>
+
+#include <pybind11/pybind11.h>
+
+namespace matplotlibcpp17::legend {
 
 struct DECL_STRUCT_ATTR Legend {
   Legend(pybind11::object obj) {
@@ -12,4 +19,6 @@ struct DECL_STRUCT_ATTR Legend {
   // for passing as python object
   pybind11::object unwrap() { return self; }
 };
-} // namespace legend
+} // namespace matplotlibcpp17::legend
+
+#endif /* MATPLOTLIBCPP17_LEGEND_H */
diff --git a/include/matplotlibcpp17/matplotlibcpp17.h b/include/matplotlibcpp17/matplotlibcpp17.h
index 8939ab8..fda7678 100644
--- a/include/matplotlibcpp17/matplotlibcpp17.h
+++ b/include/matplotlibcpp17/matplotlibcpp17.h
@@ -1,24 +1,18 @@
 #ifndef MATPLOTLIBCPP_17_H
 #define MATPLOTLIBCPP_17_H
 
-#include <pybind11/pybind11.h>
+#include <matplotlibcpp17/animation.h>
+#include <matplotlibcpp17/axes.h>
+#include <matplotlibcpp17/collections.h>
+#include <matplotlibcpp17/figure.h>
+#include <matplotlibcpp17/gridspec.h>
+#include <matplotlibcpp17/legend.h>
+#include <matplotlibcpp17/patches.h>
+#include <matplotlibcpp17/pyplot.h>
+#include <matplotlibcpp17/quiver.h>
 
 namespace matplotlibcpp17 {
 
-#include "common.h"
-
-#include "animation.h"
-#include "text.h"
-#include "container.h"
-#include "collections.h"
-#include "legend.h"
-#include "quiver.h"
-#include "axes.h"
-#include "gridspec.h"
-#include "figure.h"
-#include "patches.h"
-#include "pyplot.h"
-
 template <typename... Args> pybind11::tuple args_(Args &&... args) {
   return pybind11::make_tuple(std::forward<Args>(args)...);
 }
diff --git a/include/matplotlibcpp17/patches.h b/include/matplotlibcpp17/patches.h
index 5802d71..2a69c03 100644
--- a/include/matplotlibcpp17/patches.h
+++ b/include/matplotlibcpp17/patches.h
@@ -1,4 +1,11 @@
-namespace patches {
+#ifndef MATPLOTLIBCPP17_PATCHES_H
+#define MATPLOTLIBCPP17_PATCHES_H
+
+#include <matplotlibcpp17/common.h>
+
+#include <pybind11/pybind11.h>
+
+namespace matplotlibcpp17::patches {
 
 struct DECL_STRUCT_ATTR Circle {
   Circle(const pybind11::tuple &args = pybind11::tuple(),
@@ -58,4 +65,6 @@ struct DECL_STRUCT_ATTR Wedge {
   pybind11::object wedge_attr;
 };
 
-} // namespace patches
+} // namespace matplotlibcpp17::patches
+
+#endif /* MATPLOTLIBCPP17_PATCHES_H */
diff --git a/include/matplotlibcpp17/pyplot.h b/include/matplotlibcpp17/pyplot.h
index 2080f09..ce98b8c 100644
--- a/include/matplotlibcpp17/pyplot.h
+++ b/include/matplotlibcpp17/pyplot.h
@@ -1,4 +1,15 @@
-namespace pyplot {
+#ifndef MATPLOTLIBCPP17_PYPLOT_H
+#define MATPLOTLIBCPP17_PYPLOT_H
+
+#include <tuple>
+
+#include <matplotlibcpp17/common.h>
+#include <matplotlibcpp17/axes.h>
+#include <matplotlibcpp17/figure.h>
+
+#include <pybind11/pybind11.h>
+
+namespace matplotlibcpp17::pyplot {
 
 struct DECL_STRUCT_ATTR PyPlot {
   PyPlot() {}
@@ -175,4 +186,6 @@ PyPlot import() {
   return g_pyplot;
 }
 
-} // namespace pyplot
+} // namespace matplotlibcpp17::pyplot
+
+#endif /* MATPLOTLIBCPP17_PYPLOT_H */
diff --git a/include/matplotlibcpp17/quiver.h b/include/matplotlibcpp17/quiver.h
index 1233fef..4be6534 100644
--- a/include/matplotlibcpp17/quiver.h
+++ b/include/matplotlibcpp17/quiver.h
@@ -1,4 +1,11 @@
-namespace quiver {
+#ifndef MATPLOTLIBCPP17_QUIVER_H
+#define MATPLOTLIBCPP17_QUIVER_H
+
+#include <matplotlibcpp17/common.h>
+
+#include <pybind11/pybind11.h>
+
+namespace matplotlibcpp17::quiver {
 
 struct DECL_STRUCT_ATTR Quiver {
   Quiver(pybind11::object q) { self = q; }
@@ -15,4 +22,6 @@ struct DECL_STRUCT_ATTR QuiverKey {
   pybind11::object unwrap() { return self; }
 };
 
-} // namespace quiver
+} // namespace matplotlibcpp17::quiver
+
+#endif /* MATPLOTLIBCPP17_QUIVER_H */
diff --git a/include/matplotlibcpp17/text.h b/include/matplotlibcpp17/text.h
index d401734..48a880a 100644
--- a/include/matplotlibcpp17/text.h
+++ b/include/matplotlibcpp17/text.h
@@ -1,4 +1,11 @@
-namespace text {
+#ifndef MATPLOTLIBCPP17_TEXT_H
+#define MATPLOTLIBCPP17_TEXT_H
+
+#include <matplotlibcpp17/common.h>
+
+#include <pybind11/pybind11.h>
+
+namespace matplotlibcpp17::text {
 
 struct DECL_STRUCT_ATTR Text {
   Text(pybind11::object text) {
@@ -10,4 +17,6 @@ struct DECL_STRUCT_ATTR Text {
   pybind11::object set_rotation;
 };
 
-} // namespace text
+} // namespace matplotlibcpp17::text
+
+#endif /* MATPLOTLIBCPP17_TEXT_H */