diff --git a/src/im_mad/xen/xen.rb b/src/im_mad/xen/xen.rb
index e86b9c359e..2a514722dc 100755
--- a/src/im_mad/xen/xen.rb
+++ b/src/im_mad/xen/xen.rb
@@ -47,7 +47,7 @@ xm_text.each_line {|line|
     case columns[0]
     when 'total_memory'
         memory_info[:total]=columns[1].to_i*1024
-    when 'free_memory'
+    when 'max_free_memory'
         memory_info[:free]=columns[1].to_i*1024
     when 'nr_cpus'
         cpu_info[:total]=columns[1].to_f*100