silence a warning
diff --git a/progs/xdemos/wincopy.c b/progs/xdemos/wincopy.c
index 04fa98a..3ec67dc 100644
--- a/progs/xdemos/wincopy.c
+++ b/progs/xdemos/wincopy.c
@@ -32,7 +32,7 @@
  */
 
 
-
+#define GLX_GLXEXT_PROTOTYPES
 #include <GL/gl.h>
 #include <GL/glx.h>
 #include <X11/keysym.h>