diff --git a/prebuild.xml b/prebuild.xml
index d9d84740d4..7e5bd5bd55 100644
--- a/prebuild.xml
+++ b/prebuild.xml
@@ -1602,6 +1602,7 @@
       </Configuration>
 
       <ReferencePath>../../../../../../../bin/</ReferencePath>
+      <Reference name="System" localCopy="false"/>
       <Reference name="OpenSim.Region.ScriptEngine.Shared.CodeTools"/>
       <Reference name="nunit.framework.dll" />
       <Reference name="Tools.dll" />