diff -ru fontconfig-2.4.2.orig/src/fcxml.c fontconfig-2.4.2/src/fcxml.c
--- fontconfig-2.4.2.orig/src/fcxml.c	2006-12-02 22:54:03.000000000 +0100
+++ fontconfig-2.4.2/src/fcxml.c	2007-02-21 17:13:37.000000000 +0100
@@ -557,6 +557,9 @@
 {
     const FcObjectType	*o;
     const FcConstant	*c;
+
+    if (!expr)
+	return;
     
     switch (expr->op) {
     case FcOpInteger: