diff --git a/XenAdmin/Controls/CustomDataGraph/GraphHelpers.cs b/XenAdmin/Controls/CustomDataGraph/GraphHelpers.cs
index 2052df90a..e2fc91f8c 100644
--- a/XenAdmin/Controls/CustomDataGraph/GraphHelpers.cs
+++ b/XenAdmin/Controls/CustomDataGraph/GraphHelpers.cs
@@ -172,6 +172,9 @@ namespace XenAdmin.Controls.CustomDataGraph
 
     public static class DataSourceItemList
     {
+        private static Regex io_throughput_rw_regex = new Regex("^io_throughput_(read|write)_([a-f0-9]{8})$"); // old SR read/write datasources
+        private static Regex sr_rw_regex = new Regex("^(read|write)_([a-f0-9]{8})$"); // replacement SR read/write datasources
+
         public static List<DataSourceItem> BuildList(IXenObject xenObject, List<Data_source> dataSources)
         {
             List<DataSourceItem> dataSourceItems = new List<DataSourceItem>();
@@ -194,9 +197,6 @@ namespace XenAdmin.Controls.CustomDataGraph
             }
 
             // Filter old datasources only if we have their replacement ones
-            Regex io_throughput_rw_regex = new Regex("^io_throughput_(read|write)_([a-f0-9]{8})$"); // old datasources
-            Regex sr_rw_regex = new Regex("^(read|write)_([a-f0-9]{8})$"); // replacement datasources
-
             if (dataSourceItems.Any(dsi => sr_rw_regex.IsMatch(dsi.DataSource.name_label)))
             {
                 // Remove any old style data sources