diff -rupN old/glxcmds.c new/glxcmds.c
--- old/src/glx/x11/glxcmds.c	2009-08-17 22:09:54.545156000 +0200
+++ new/src/glx/x11/glxcmds.c	2009-08-17 22:11:44.589154771 +0200
@@ -1395,7 +1395,7 @@ glXChooseVisual(Display * dpy, int scree
                                   &visualTemplate, &i);
 
          if (newList) {
-            Xfree(visualList);
+            if(visualList) Xfree(visualList);
             visualList = newList;
             best_config = modes;
          }