Index: lib/strobj.c
--- lib/strobj.c.orig	2003-12-23 05:22:53.000000000 +0100
+++ lib/strobj.c	2004-05-21 09:44:36.000000000 +0200
@@ -165,6 +165,7 @@
 
 int string_appendvf (String *sobj, const char *fmt, va_list args)
 {
+	va_list args_cpy;
 	int written = 0;
 
 	if (!sobj)
@@ -186,7 +187,15 @@
 		{
 			max = sobj->alloc - sobj->len;
 
-			written = vsnprintf (sobj->str + sobj->len, max, fmt, args);
+			/*
+			 * We have to make a copy of the va_list because we may pass this
+			 * point multiple times. Note that simply calling va_start again is
+			 * not a good idea since the va_start/va_end should be in the same
+			 * stack frame because of some obscure implementations.
+			 */
+			va_copy (args_cpy, args);
+			written = vsnprintf (sobj->str + sobj->len, max, fmt, args_cpy);
+			va_end (args_cpy);
 
 			/*
 			 * Some implementations use -1 to indicate an inability to write