diff -ur xrootd-3.0.3.orig/configure.ac xrootd-3.0.3/configure.ac
--- xrootd-3.0.3.orig/configure.ac	2011-04-11 13:24:37.000000000 +0200
+++ xrootd-3.0.3/configure.ac	2011-05-02 13:50:01.879165899 +0200
@@ -252,7 +252,7 @@
 [AC_TRY_RUN([
 int main()
 {
-    unsigned long val = 111, tmp, *mem = &val;
+    unsigned long long val = 111, tmp, *mem = &val;
 
     if (__sync_fetch_and_add(&val, 111) != 111 || val != 222) return 1;
     if (__sync_add_and_fetch(&val, 111) != 333)               return 1;