diff -ruN arts-1.1.4.old/flow/gsl/gslglib.h arts-1.1.4/flow/gsl/gslglib.h
--- arts-1.1.4.old/flow/gsl/gslglib.h	2003-07-13 15:33:38.000000000 -0400
+++ arts-1.1.4/flow/gsl/gslglib.h	2003-09-27 18:12:04.368204936 -0400
@@ -507,6 +507,9 @@
 #if !defined (G_VA_COPY)
 #  if defined (__GNUC__) && ( defined (__PPC__) || defined (__s390__) ) && (defined (_CALL_SYSV) || defined (_WIN32) || defined (__s390__) )
 #    define G_VA_COPY(ap1, ap2)   (*(ap1) = *(ap2))
+#  elif defined (__x86_64__)
+#    include <stdarg.h>
+#    define G_VA_COPY(ap1, ap2) __va_copy((ap1), (ap2))
 #  elif defined (G_VA_COPY_AS_ARRAY)
 #    define G_VA_COPY(ap1, ap2)   g_memmove ((ap1), (ap2), sizeof (va_list))
 #  else /* va_list is a pointer */