--- ruby-2.0.0-p247.orig/missing/isnan.c	2010-07-28 10:12:01.000000000 +0200
+++ ruby-2.0.0-p247/missing/isnan.c	2013-10-24 09:02:41.000000000 +0200
@@ -4,6 +4,8 @@
 
 static int double_ne(double n1, double n2);
 
+#undef isnan
+
 int
 isnan(double n)
 {