diff --git a/sdl-opengl-vbo/checkGLError.h b/sdl-opengl-vbo/checkGLError.h
index b853813..cdf7bde 100644
--- a/sdl-opengl-vbo/checkGLError.h
+++ b/sdl-opengl-vbo/checkGLError.h
@@ -5,6 +5,7 @@
 #include <GL/gl.h>
 
 #define checkGLError() _checkGLError(__FILE__, __LINE__)
+#define GL_CHECK(x) ({x; checkGLError();})
 
 GLenum _checkGLError(const char *fname, int lineno);
 
diff --git a/sdl-opengl-vbo/sdl-opengl-vbo.cc b/sdl-opengl-vbo/sdl-opengl-vbo.cc
index ff59ea7..1ee1ee0 100644
--- a/sdl-opengl-vbo/sdl-opengl-vbo.cc
+++ b/sdl-opengl-vbo/sdl-opengl-vbo.cc
@@ -10,12 +10,13 @@
 #define HEIGHT  500
 
 #define ADDR_DIFF(x, y) ((unsigned long) (y) - (unsigned long) (x))
-#define GL_CHECK(x) ({x; checkGLError();})
 
 void init(void)
 {
     GL_CHECK(glClearColor (0.0, 0.0, 0.0, 0.0));
     GL_CHECK(glEnable(GL_DEPTH_TEST));
+    GL_CHECK(glEnableClientState(GL_VERTEX_ARRAY));
+    GL_CHECK(glEnableClientState(GL_COLOR_ARRAY));
     GL_CHECK(glShadeModel(GL_SMOOTH));
     GL_CHECK(glViewport(0, 0, WIDTH, HEIGHT));
     GL_CHECK(glMatrixMode(GL_PROJECTION));
@@ -35,7 +36,7 @@ void display(void)
         {{0.8, 0.8, 0.0, 1.0}, {0.0, 0.0, 1.0, 1.0}},
         {{-0.8, 0.8, 0.0, 1.0}, {0.0, 0.4, 1.0, 1.0}}
     };
-    static const GLbyte indexes[] = {1, 0, 2, 3};
+    static const GLushort indexes[] = {1, 0, 2, 3};
     GLuint buffers[2];
     GL_CHECK(glGenBuffers(sizeof(buffers)/sizeof(buffers[0]), buffers));
     GL_CHECK(glBindBuffer(GL_ARRAY_BUFFER, buffers[0]));
@@ -50,7 +51,7 @@ void display(void)
             (void *) ADDR_DIFF(&data, &data[0][0][0])));
     GL_CHECK(glColorPointer(4, GL_FLOAT, ADDR_DIFF(&data[0], &data[1]),
             (void *) ADDR_DIFF(&data, &data[0][1][0])));
-    GL_CHECK(glDrawElements(GL_TRIANGLE_STRIP, 4, GL_UNSIGNED_BYTE, NULL));
+    GL_CHECK(glDrawElements(GL_TRIANGLE_STRIP, 4, GL_UNSIGNED_SHORT, NULL));
     SDL_GL_SwapBuffers();
 }