diff --git a/progs/demos/tunnel.c b/progs/demos/tunnel.c
index efc007c..4158a25 100644
--- a/progs/demos/tunnel.c
+++ b/progs/demos/tunnel.c
@@ -460,7 +460,7 @@ draw(void)
    glPopMatrix();
    glMatrixMode(GL_MODELVIEW);
 
-   glutSwapBuffers();
+   glFlush();
 
    Frames++;
    {
@@ -501,6 +501,8 @@ main(int ac, char **av)
       return -1;
    }
 
+   glDrawBuffer(GL_FRONT);
+
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(80.0, WIDTH / (float) HEIGHT, 1.0, 50.0);