--- configure.ac
+++ configure.ac
@@ -188,8 +188,11 @@
 
 dnl
 dnl check for Cg
-dnlCG_LD
-if test "${have_fltk}" = yes; then
+dnl CG_LD
+AC_ARG_ENABLE(nvidia, AC_HELP_STRING([--enable-nvidia],
+  [enable nvidia cg support [[default=check]]]), [want_nvidia="${enableval}"], [want_nvidia=yes])
+
+if test "${have_fltk}" = yes -a "${want_nvidia}" != "no"; then
   AM_PATH_CG(have_cg=yes, have_cg=no)
   if test "${have_cg}" = yes; then
     AC_DEFINE(HAVE_FRAGMENT_SHADERS)