diff -up CriticalMass-1.5/utilsgl/GLee.h~ CriticalMass-1.5/utilsgl/GLee.h

--- CriticalMass-1.5/utilsgl/GLee.h~	2010-10-17 03:09:51.000000000 +0200

+++ CriticalMass-1.5/utilsgl/GLee.h	2019-02-16 23:38:55.538912671 +0100

@@ -68,6 +68,7 @@

 #else // GLX

 	#define __glext_h_  /* prevent glext.h from being included  */

 	#define __glxext_h_ /* prevent glxext.h from being included */

+	#define GL_GLEXT_PROTOTYPES

 	#define GLX_GLXEXT_PROTOTYPES

 	#include <GL/gl.h>

 	#include <GL/glx.h>